Move to Symfony Flex

The structure changed completely.
Bundles are gone. Everything is flatten in the folder `src`.
I separated import & api controllers to avoid _pollution_ in the main controller folder.

scripts/webpack/dev.js

@@ -0,0 +1,58 @@
+const { merge } = require('webpack-merge');
+const ESLintPlugin = require('eslint-webpack-plugin');
+const commonConfig = require('./common');
+
+module.exports = merge(commonConfig, {
+  devtool: 'eval-source-map',
+  output: {
+    filename: '[name].dev.js',
+  },
+  mode: 'development',
+  devServer: {
+    static: {
+      directory: './public',
+    },
+  },
+  plugins: [
+    new ESLintPlugin(),
+  ],
+  module: {
+    rules: [
+      {
+        test: /\.js$/,
+        exclude: /(node_modules)/,
+        use: {
+          loader: 'babel-loader',
+          options: {
+            presets: ['@babel/preset-env'],
+          },
+        },
+      },
+      {
+        test: /\.(s)?css$/,
+        use: [
+          'style-loader',
+          {
+            loader: 'css-loader',
+            options: {
+              importLoaders: 1,
+            },
+          },
+          {
+            loader: 'postcss-loader',
+            options: {
+              postcssOptions: {
+                plugins: ['autoprefixer'],
+              },
+            },
+          },
+          'sass-loader',
+        ],
+      },
+      {
+        test: /\.(jpg|png|gif|svg|ico|eot|ttf|woff|woff2)$/,
+        type: 'asset/inline',
+      },
+    ],
+  },
+});