lint & example fixes (#3160)

* fix import extensions of eslint

* revert next.config.cjs

* fix eslint globbing

* add migrating to docs’ sidebar

* fix prettier error on Contributing.md

* put quotes for glob matching for windows user

* remove type: module from  package.json

site/next.config.js

@@ -0,0 +1,23 @@
+const fs = require('fs')
+const path = require('path')
+
+module.exports = {
+  exportPathMap: async (defaultPathMap, config) => {
+    const { dir } = config
+    const examples = fs.readdirSync(path.resolve(dir, 'examples'))
+    const pages = {
+      '/': { page: '/' },
+    }
+
+    for (const file of examples) {
+      if (!file.endsWith('.js')) {
+        continue
+      }
+
+      const example = file.replace('.js', '')
+      pages[`/examples/${example}`] = { page: '/examples/[example]', example }
+    }
+
+    return pages
+  },
+}