Use webpack for building static assets

core/admin/webpack.config.js

@@ -0,0 +1,56 @@
+var path = require("path");
+var webpack = require("webpack");
+var css = require("mini-css-extract-plugin");
+
+module.exports = {
+    mode: "development",
+    entry: {
+        app: "./assets/app.js",
+        vendor: "./assets/vendor.js"
+    },
+    output: {
+        path: path.resolve(__dirname, "mailu/ui/static/"),
+        filename: "[name].js",
+        publicPath: "/static"
+    },
+    module: {
+        rules: [
+            {
+                test: /\.js$/,
+                use: {
+                    loader: "babel-loader",
+                    options: {
+                        presets: ['@babel/preset-env']
+                    }
+                }
+            },
+            {
+                test: /\.scss$/,
+                use: [css.loader, 'css-loader', 'sass-loader']
+            },
+            {
+                test: /\.less$/,
+                use: [css.loader, 'css-loader', 'less-loader']
+            },
+            {
+                test: /\.css$/,
+                use: [css.loader, 'css-loader']
+            },
+            {
+                test: /\.woff($|\?)|\.woff2($|\?)|\.ttf($|\?)|\.eot($|\?)|\.svg($|\?)/,
+                use: ['url-loader']
+            }
+        ]
+    },
+    plugins: [
+	      new css({
+	          filename: "[name].css",
+	          chunkFilename: "[id].css"
+	      }),
+        new webpack.ProvidePlugin({
+            $: "jquery",
+            jQuery: "jquery"
+        })
+    ]
+}
+