switch to rollup for easier build config

package.json

@@ -26,30 +26,29 @@
   "devDependencies": {
     "@babel/core": "^7.8.7",
     "@babel/preset-env": "^7.8.7",
+    "@rollup/plugin-node-resolve": "^7.1.3",
     "babel-eslint": "^10.1.0",
-    "babel-loader": "^8.1.0",
     "colors": "^1.4.0",
     "express": "^4.17.1",
     "glob": "^7.1.6",
     "gulp": "^4.0.2",
     "gulp-autoprefixer": "^7.0.1",
-    "gulp-babel": "^8.0.0",
     "gulp-clean-css": "^4.2.0",
     "gulp-connect": "^5.7.0",
     "gulp-eslint": "^6.0.0",
     "gulp-header": "^2.0.9",
-    "gulp-rename": "^2.0.0",
     "gulp-sass": "^4.0.2",
     "gulp-tap": "^2.0.0",
-    "gulp-uglify": "^3.0.2",
     "gulp-zip": "^5.0.1",
     "mustache": "^4.0.0",
     "node-qunit-puppeteer": "^2.0.1",
+    "rollup": "^2.6.1",
+    "rollup-plugin-babel": "^4.4.0",
+    "rollup-plugin-terser": "^5.3.0",
     "socket.io": "^2.3.0",
-    "webpack-stream": "^5.2.1",
     "yargs": "^15.1.0"
   },
-  "browserslist": "last 2 versions, > 0.5%, not dead",
+  "browserslist": "> 0.5%, IE 11, not dead",
   "eslintConfig": {
     "env": {
       "browser": true,
@@ -89,6 +88,6 @@
     }
   },
   "dependencies": {
-    "highlight.js": "^9.18.1"
+    "core-js": "^3.6.5"
   }
 }