chore(build): try to build demo and docs (#3434)

platform/app/.webpack/rules/extractStyleChunks.js

@@ -0,0 +1,21 @@
+const ExtractCssChunksPlugin = require('extract-css-chunks-webpack-plugin');
+
+function extractStyleChunks(isProdBuild) {
+  return [
+    {
+      test: /\.(sa|sc|c)ss$/,
+      use: [
+        {
+          loader: ExtractCssChunksPlugin.loader,
+          options: {
+            hot: !isProdBuild,
+          },
+        },
+        'css-loader',
+        'postcss-loader'
+      ],
+    },
+  ];
+}
+
+module.exports = extractStyleChunks;