build: convert the build pipeline to PostCSS

This conversion to PostCSS eliminates several of the npm scripts that we previously needed by using
PostCSS plugins.

Here's the conversion chart:

| Original script    | PostCSS plugin replacement |
| ------------------ | -------------------------- |
| `build:sass`       | `postcss-node-sass`        |
| `build:autoprefix` | `postcss-preset-env`       |
| `build:cleancss`   | `postcss-clean`            |

package-lock.json

@@ -990,6 +990,12 @@
         "find-up": "^2.1.0"
       }
     },
+    "@csstools/convert-colors": {
+      "version": "1.4.0",
+      "resolved": "https://registry.npmjs.org/@csstools/convert-colors/-/convert-colors-1.4.0.tgz",
+      "integrity": "sha512-5a6wqoJV/xEdbRNKVo6I4hO3VjyDq//8q2f9I6PBAvMesJHFauXDorcNCsr9RzvsZnaWi5NYCcfyqP1QeFHFbw==",
+      "dev": true
+    },
     "@emotion/babel-utils": {
       "version": "0.6.10",
       "resolved": "https://registry.npmjs.org/@emotion/babel-utils/-/babel-utils-0.6.10.tgz",
@@ -4169,29 +4175,6 @@
         "wrap-ansi": "^2.0.0"
       }
     },
-    "clone-deep": {
-      "version": "2.0.2",
-      "resolved": "https://registry.npmjs.org/clone-deep/-/clone-deep-2.0.2.tgz",
-      "integrity": "sha512-SZegPTKjCgpQH63E+eN6mVEEPdQBOUzjyJm5Pora4lrwWRFS8I0QAxV/KD6vV/i0WuijHZWQC1fMsPEdxfdVCQ==",
-      "dev": true,
-      "requires": {
-        "for-own": "^1.0.0",
-        "is-plain-object": "^2.0.4",
-        "kind-of": "^6.0.0",
-        "shallow-clone": "^1.0.0"
-      },
-      "dependencies": {
-        "for-own": {
-          "version": "1.0.0",
-          "resolved": "https://registry.npmjs.org/for-own/-/for-own-1.0.0.tgz",
-          "integrity": "sha1-xjMy9BXO3EsE2/5wz4NklMU8tEs=",
-          "dev": true,
-          "requires": {
-            "for-in": "^1.0.1"
-          }
-        }
-      }
-    },
     "clone-regexp": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/clone-regexp/-/clone-regexp-1.0.1.tgz",
@@ -4719,6 +4702,44 @@
         "randomfill": "^1.0.3"
       }
     },
+    "css-blank-pseudo": {
+      "version": "0.1.4",
+      "resolved": "https://registry.npmjs.org/css-blank-pseudo/-/css-blank-pseudo-0.1.4.tgz",
+      "integrity": "sha512-LHz35Hr83dnFeipc7oqFDmsjHdljj3TQtxGGiNWSOsTLIAubSm4TEz8qCaKFpk7idaQ1GfWscF4E6mgpBysA1w==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.5"
+      }
+    },
+    "css-has-pseudo": {
+      "version": "0.10.0",
+      "resolved": "https://registry.npmjs.org/css-has-pseudo/-/css-has-pseudo-0.10.0.tgz",
+      "integrity": "sha512-Z8hnfsZu4o/kt+AuFzeGpLVhFOGO9mluyHBaA2bA8aCGTwah5sT3WV/fTHH8UNZUytOIImuGPrl/prlb4oX4qQ==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.6",
+        "postcss-selector-parser": "^5.0.0-rc.4"
+      },
+      "dependencies": {
+        "cssesc": {
+          "version": "2.0.0",
+          "resolved": "https://registry.npmjs.org/cssesc/-/cssesc-2.0.0.tgz",
+          "integrity": "sha512-MsCAG1z9lPdoO/IUMLSBWBSVxVtJ1395VGIQ+Fc2gNdkQ1hNDnQdw3YhA71WJCBW1vdwA0cAnk/DnW6bqoEUYg==",
+          "dev": true
+        },
+        "postcss-selector-parser": {
+          "version": "5.0.0",
+          "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-5.0.0.tgz",
+          "integrity": "sha512-w+zLE5Jhg6Liz8+rQOWEAwtwkyqpfnmsinXjXg6cY7YIONZZtgvE0v2O0uhQBs0peNomOJwWRKt6JBfTdTd3OQ==",
+          "dev": true,
+          "requires": {
+            "cssesc": "^2.0.0",
+            "indexes-of": "^1.0.1",
+            "uniq": "^1.0.1"
+          }
+        }
+      }
+    },
     "css-loader": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/css-loader/-/css-loader-2.1.0.tgz",
@@ -4788,6 +4809,15 @@
         }
       }
     },
+    "css-prefers-color-scheme": {
+      "version": "3.1.1",
+      "resolved": "https://registry.npmjs.org/css-prefers-color-scheme/-/css-prefers-color-scheme-3.1.1.tgz",
+      "integrity": "sha512-MTu6+tMs9S3EUqzmqLXEcgNRbNkkD/TGFvowpeoWJn5Vfq7FMgsmRQs9X5NXAURiOBmOxm/lLjsDNXDE6k9bhg==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.5"
+      }
+    },
     "css-select": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/css-select/-/css-select-1.2.0.tgz",
@@ -4851,6 +4881,12 @@
       "integrity": "sha512-a+EPoD+uZiNfh+5fxw2nO9QwFa6nJe2Or35fGY6Ipw1R3R4AGz1d1TEZrCegvw2YTmZ0jXirGYlzxxpYSHwpEg==",
       "dev": true
     },
+    "cssdb": {
+      "version": "4.4.0",
+      "resolved": "https://registry.npmjs.org/cssdb/-/cssdb-4.4.0.tgz",
+      "integrity": "sha512-LsTAR1JPEM9TpGhl/0p3nQecC2LJ0kD8X5YARu1hk/9I1gril5vDtMZyNxcEpxxDj34YNck/ucjuoUd66K03oQ==",
+      "dev": true
+    },
     "cssesc": {
       "version": "0.1.0",
       "resolved": "https://registry.npmjs.org/cssesc/-/cssesc-0.1.0.tgz",
@@ -6330,6 +6366,12 @@
         }
       }
     },
+    "file-type": {
+      "version": "11.0.0",
+      "resolved": "https://registry.npmjs.org/file-type/-/file-type-11.0.0.tgz",
+      "integrity": "sha512-ixd0mHkDO8KJ1S+ANTM+cZoZgL+TB0txLMm9KjTndfOjFYuRmrUcOtmSEm+e9s7wrynZOvvRD/8LwMQ6a24Irg==",
+      "dev": true
+    },
     "filesize": {
       "version": "3.6.1",
       "resolved": "https://registry.npmjs.org/filesize/-/filesize-3.6.1.tgz",
@@ -6481,6 +6523,12 @@
       "integrity": "sha512-R+H8IZclI8AAkSBRQJLVOsxwAoHd6WC40b4QTNWIjzAa6BXOBfQcM587MXDTVPeYaopFNWHUFLx7eNmHDSxMWg==",
       "dev": true
     },
+    "flatten": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/flatten/-/flatten-1.0.2.tgz",
+      "integrity": "sha1-2uRqnXj74lKSJYzB54CkHZXAN4I=",
+      "dev": true
+    },
     "flush-write-stream": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/flush-write-stream/-/flush-write-stream-1.1.1.tgz",
@@ -9336,12 +9384,6 @@
       "integrity": "sha1-7dFMgk4sycHgsKG0K7UhBRakJDg=",
       "dev": true
     },
-    "lodash.tail": {
-      "version": "4.1.1",
-      "resolved": "https://registry.npmjs.org/lodash.tail/-/lodash.tail-4.1.1.tgz",
-      "integrity": "sha1-0jM6NtnncXyK0vfKyv7HwytERmQ=",
-      "dev": true
-    },
     "lodash.template": {
       "version": "4.4.0",
       "resolved": "https://registry.npmjs.org/lodash.template/-/lodash.template-4.4.0.tgz",
@@ -9695,6 +9737,23 @@
       "integrity": "sha1-sAqqVW3YtEVoFQ7J0blT8/kMu2E=",
       "dev": true
     },
+    "merge-source-map": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/merge-source-map/-/merge-source-map-1.1.0.tgz",
+      "integrity": "sha512-Qkcp7P2ygktpMPh2mCQZaf3jhN6D3Z/qVZHSdWvQ+2Ef5HgRAPBO57A77+ENm0CPx2+1Ce/MYKi3ymqdfuqibw==",
+      "dev": true,
+      "requires": {
+        "source-map": "^0.6.1"
+      },
+      "dependencies": {
+        "source-map": {
+          "version": "0.6.1",
+          "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.6.1.tgz",
+          "integrity": "sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==",
+          "dev": true
+        }
+      }
+    },
     "merge2": {
       "version": "1.2.3",
       "resolved": "https://registry.npmjs.org/merge2/-/merge2-1.2.3.tgz",
@@ -9850,24 +9909,6 @@
         }
       }
     },
-    "mixin-object": {
-      "version": "2.0.1",
-      "resolved": "https://registry.npmjs.org/mixin-object/-/mixin-object-2.0.1.tgz",
-      "integrity": "sha1-T7lJRB2rGCVA8f4DW6YOGUel5X4=",
-      "dev": true,
-      "requires": {
-        "for-in": "^0.1.3",
-        "is-extendable": "^0.1.1"
-      },
-      "dependencies": {
-        "for-in": {
-          "version": "0.1.8",
-          "resolved": "https://registry.npmjs.org/for-in/-/for-in-0.1.8.tgz",
-          "integrity": "sha1-2Hc5COMSVhCZUrH9ubP6hn0ndeE=",
-          "dev": true
-        }
-      }
-    },
     "mkdirp": {
       "version": "0.5.1",
       "resolved": "https://registry.npmjs.org/mkdirp/-/mkdirp-0.5.1.tgz",
@@ -14627,6 +14668,84 @@
         }
       }
     },
+    "postcss-attribute-case-insensitive": {
+      "version": "4.0.1",
+      "resolved": "https://registry.npmjs.org/postcss-attribute-case-insensitive/-/postcss-attribute-case-insensitive-4.0.1.tgz",
+      "integrity": "sha512-L2YKB3vF4PetdTIthQVeT+7YiSzMoNMLLYxPXXppOOP7NoazEAy45sh2LvJ8leCQjfBcfkYQs8TtCcQjeZTp8A==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.2",
+        "postcss-selector-parser": "^5.0.0"
+      },
+      "dependencies": {
+        "cssesc": {
+          "version": "2.0.0",
+          "resolved": "https://registry.npmjs.org/cssesc/-/cssesc-2.0.0.tgz",
+          "integrity": "sha512-MsCAG1z9lPdoO/IUMLSBWBSVxVtJ1395VGIQ+Fc2gNdkQ1hNDnQdw3YhA71WJCBW1vdwA0cAnk/DnW6bqoEUYg==",
+          "dev": true
+        },
+        "postcss-selector-parser": {
+          "version": "5.0.0",
+          "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-5.0.0.tgz",
+          "integrity": "sha512-w+zLE5Jhg6Liz8+rQOWEAwtwkyqpfnmsinXjXg6cY7YIONZZtgvE0v2O0uhQBs0peNomOJwWRKt6JBfTdTd3OQ==",
+          "dev": true,
+          "requires": {
+            "cssesc": "^2.0.0",
+            "indexes-of": "^1.0.1",
+            "uniq": "^1.0.1"
+          }
+        }
+      }
+    },
+    "postcss-browser-reporter": {
+      "version": "0.6.0",
+      "resolved": "https://registry.npmjs.org/postcss-browser-reporter/-/postcss-browser-reporter-0.6.0.tgz",
+      "integrity": "sha512-61gzk4wgthOIen4TRURzYYVVIszyvcorkYmD40CopdM8cdwJaCTDMYo/y8HQqjTPqyelw7r2ptncmR9xrWpVnw==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.14"
+      }
+    },
+    "postcss-clean": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/postcss-clean/-/postcss-clean-1.1.0.tgz",
+      "integrity": "sha512-83g3GqMbCM5NL6MlbbPLJ/m2NrUepBF44MoDk4Gt04QGXeXKh9+ilQa0DzLnYnvqYHQCw83nckuEzBFr2muwbg==",
+      "dev": true,
+      "requires": {
+        "clean-css": "^4.x",
+        "postcss": "^6.x"
+      },
+      "dependencies": {
+        "chalk": {
+          "version": "2.4.2",
+          "resolved": "https://registry.npmjs.org/chalk/-/chalk-2.4.2.tgz",
+          "integrity": "sha512-Mti+f9lpJNcwF4tWV8/OrTTtF1gZi+f8FqlyAdouralcFWFQWF2+NgCHShjkCb+IFBLq9buZwE1xckQU4peSuQ==",
+          "dev": true,
+          "requires": {
+            "ansi-styles": "^3.2.1",
+            "escape-string-regexp": "^1.0.5",
+            "supports-color": "^5.3.0"
+          }
+        },
+        "postcss": {
+          "version": "6.0.23",
+          "resolved": "https://registry.npmjs.org/postcss/-/postcss-6.0.23.tgz",
+          "integrity": "sha512-soOk1h6J3VMTZtVeVpv15/Hpdl2cBLX3CAw4TAbkpTJiNPk9YP/zWcD1ND+xEtvyuuvKzbxliTOIyvkSeSJ6ag==",
+          "dev": true,
+          "requires": {
+            "chalk": "^2.4.1",
+            "source-map": "^0.6.1",
+            "supports-color": "^5.4.0"
+          }
+        },
+        "source-map": {
+          "version": "0.6.1",
+          "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.6.1.tgz",
+          "integrity": "sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==",
+          "dev": true
+        }
+      }
+    },
     "postcss-cli": {
       "version": "6.1.1",
       "resolved": "https://registry.npmjs.org/postcss-cli/-/postcss-cli-6.1.1.tgz",
@@ -14655,6 +14774,155 @@
         }
       }
     },
+    "postcss-color-functional-notation": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/postcss-color-functional-notation/-/postcss-color-functional-notation-2.0.1.tgz",
+      "integrity": "sha512-ZBARCypjEDofW4P6IdPVTLhDNXPRn8T2s1zHbZidW6rPaaZvcnCS2soYFIQJrMZSxiePJ2XIYTlcb2ztr/eT2g==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.2",
+        "postcss-values-parser": "^2.0.0"
+      }
+    },
+    "postcss-color-gray": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/postcss-color-gray/-/postcss-color-gray-5.0.0.tgz",
+      "integrity": "sha512-q6BuRnAGKM/ZRpfDascZlIZPjvwsRye7UDNalqVz3s7GDxMtqPY6+Q871liNxsonUw8oC61OG+PSaysYpl1bnw==",
+      "dev": true,
+      "requires": {
+        "@csstools/convert-colors": "^1.4.0",
+        "postcss": "^7.0.5",
+        "postcss-values-parser": "^2.0.0"
+      }
+    },
+    "postcss-color-hex-alpha": {
+      "version": "5.0.3",
+      "resolved": "https://registry.npmjs.org/postcss-color-hex-alpha/-/postcss-color-hex-alpha-5.0.3.tgz",
+      "integrity": "sha512-PF4GDel8q3kkreVXKLAGNpHKilXsZ6xuu+mOQMHWHLPNyjiUBOr75sp5ZKJfmv1MCus5/DWUGcK9hm6qHEnXYw==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.14",
+        "postcss-values-parser": "^2.0.1"
+      }
+    },
+    "postcss-color-mod-function": {
+      "version": "3.0.3",
+      "resolved": "https://registry.npmjs.org/postcss-color-mod-function/-/postcss-color-mod-function-3.0.3.tgz",
+      "integrity": "sha512-YP4VG+xufxaVtzV6ZmhEtc+/aTXH3d0JLpnYfxqTvwZPbJhWqp8bSY3nfNzNRFLgB4XSaBA82OE4VjOOKpCdVQ==",
+      "dev": true,
+      "requires": {
+        "@csstools/convert-colors": "^1.4.0",
+        "postcss": "^7.0.2",
+        "postcss-values-parser": "^2.0.0"
+      }
+    },
+    "postcss-color-rebeccapurple": {
+      "version": "4.0.1",
+      "resolved": "https://registry.npmjs.org/postcss-color-rebeccapurple/-/postcss-color-rebeccapurple-4.0.1.tgz",
+      "integrity": "sha512-aAe3OhkS6qJXBbqzvZth2Au4V3KieR5sRQ4ptb2b2O8wgvB3SJBsdG+jsn2BZbbwekDG8nTfcCNKcSfe/lEy8g==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.2",
+        "postcss-values-parser": "^2.0.0"
+      }
+    },
+    "postcss-custom-media": {
+      "version": "7.0.8",
+      "resolved": "https://registry.npmjs.org/postcss-custom-media/-/postcss-custom-media-7.0.8.tgz",
+      "integrity": "sha512-c9s5iX0Ge15o00HKbuRuTqNndsJUbaXdiNsksnVH8H4gdc+zbLzr/UasOwNG6CTDpLFekVY4672eWdiiWu2GUg==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.14"
+      }
+    },
+    "postcss-custom-properties": {
+      "version": "8.0.10",
+      "resolved": "https://registry.npmjs.org/postcss-custom-properties/-/postcss-custom-properties-8.0.10.tgz",
+      "integrity": "sha512-GDL0dyd7++goDR4SSasYdRNNvp4Gqy1XMzcCnTijiph7VB27XXpJ8bW/AI0i2VSBZ55TpdGhMr37kMSpRfYD0Q==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.14",
+        "postcss-values-parser": "^2.0.1"
+      }
+    },
+    "postcss-custom-selectors": {
+      "version": "5.1.2",
+      "resolved": "https://registry.npmjs.org/postcss-custom-selectors/-/postcss-custom-selectors-5.1.2.tgz",
+      "integrity": "sha512-DSGDhqinCqXqlS4R7KGxL1OSycd1lydugJ1ky4iRXPHdBRiozyMHrdu0H3o7qNOCiZwySZTUI5MV0T8QhCLu+w==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.2",
+        "postcss-selector-parser": "^5.0.0-rc.3"
+      },
+      "dependencies": {
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+          "version": "2.0.0",
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+        },
+        "postcss-selector-parser": {
+          "version": "5.0.0",
+          "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-5.0.0.tgz",
+          "integrity": "sha512-w+zLE5Jhg6Liz8+rQOWEAwtwkyqpfnmsinXjXg6cY7YIONZZtgvE0v2O0uhQBs0peNomOJwWRKt6JBfTdTd3OQ==",
+          "dev": true,
+          "requires": {
+            "cssesc": "^2.0.0",
+            "indexes-of": "^1.0.1",
+            "uniq": "^1.0.1"
+          }
+        }
+      }
+    },
+    "postcss-dir-pseudo-class": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/postcss-dir-pseudo-class/-/postcss-dir-pseudo-class-5.0.0.tgz",
+      "integrity": "sha512-3pm4oq8HYWMZePJY+5ANriPs3P07q+LW6FAdTlkFH2XqDdP4HeeJYMOzn0HYLhRSjBO3fhiqSwwU9xEULSrPgw==",
+      "dev": true,
+      "requires": {
+        "postcss": "^7.0.2",
+        "postcss-selector-parser": "^5.0.0-rc.3"
+      },
+      "dependencies": {
+        "cssesc": {
+          "version": "2.0.0",
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+          "dev": true
+        },
+        "postcss-selector-parser": {
+          "version": "5.0.0",
+          "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-5.0.0.tgz",
+          "integrity": "sha512-w+zLE5Jhg6Liz8+rQOWEAwtwkyqpfnmsinXjXg6cY7YIONZZtgvE0v2O0uhQBs0peNomOJwWRKt6JBfTdTd3OQ==",
+          "dev": true,
+          "requires": {
+            "cssesc": "^2.0.0",
+            "indexes-of": "^1.0.1",
+            "uniq": "^1.0.1"
+          }
+        }
+      }
+    },
+    "postcss-double-position-gradients": {
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package.json

@@ -2,23 +2,14 @@
   "name": "nes.css",
   "description": "NES.css is NES-style CSS Framework.",
   "scripts": {
-    "watch": "npm run build:sass -- --watch",
+    "watch": "npm run build:main -- --watch",
     "// Build task": "",
     "build": "run-p build:core build:main",
-    "build:core": "npm run build:sass-core && npm run build:autoprefix-core && npm run build:cleancss-core",
+    "build:core": "postcss scss/nes-core.scss --output css/nes-core.css",
-    "build:main": "npm run build:sass && npm run build:autoprefix && npm run build:cleancss",
+    "build:main": "postcss scss/nes.scss --output css/nes.css -m",
     "prebuild": "run-p prebuild:*",
     "prebuild:stylelint": "npm run stylelint -- --fix",
-    "prebuild:clean": "rimraf css",
     "postbuild": "npm run build:storybook",
-    "// For nes.css": "",
-    "build:sass": "node-sass --output-style expanded --source-map true --functions scripts/scssFunctions.js scss/nes.scss css/nes.css",
-    "build:autoprefix": "postcss --use autoprefixer --map false --output css/nes.css css/nes.css",
-    "build:cleancss": "cleancss -o css/nes.min.css css/nes.css",
-    "// For nes-core.css": "",
-    "build:sass-core": "node-sass --output-style expanded --source-map true --functions scripts/scssFunctions.js scss/nes-core.scss css/nes-core.css",
-    "build:autoprefix-core": "postcss --use autoprefixer --map false --output css/nes-core.css css/nes-core.css",
-    "build:cleancss-core": "cleancss -o css/nes-core.min.css css/nes-core.css",
     "// Misc": "",
     "stylelint": "stylelint scss/**/*.scss",
     "storybook": "start-storybook -p 6006",
@@ -72,8 +63,6 @@
     "postcss-node-sass": "^2.1.8",
     "postcss-preset-env": "^6.6.0",
     "prettier": "^1.15.2",
-    "rimraf": "^2.6.2",
-    "sass-loader": "^7.1.0",
     "semantic-release": "^15.13.13",
     "style-loader": "^0.23.1",
     "stylelint": "^9.5.0",