feat: improve the cacheability of the vendor bundle

BREAKING CHANGE: The webpack runtime has moved into a separate file. Therefore you need to add a reference to that file into your HTML / Handlebars file(s) before the vendor bundle:

```html
<!-- webpack runtime JS -->
@@runtime.js

<!-- Vendor JS -->
@@vendor.js

<!-- Own JS -->
@@app.js
```

See <https://developers.google.com/web/fundamentals/performance/webpack/use-long-term-caching#webpack_runtime_code> for details about the why.

Author: mischah

app/templates/build/webpack/config.optimization.js

@@ -1,6 +1,9 @@
 import UglifyJSPlugin from 'uglifyjs-webpack-plugin';
 
 export const optimization = {
+	runtimeChunk: {
+		name: 'runtime'
+	},
 	splitChunks: {
 		cacheGroups: {
 			commons: {

app/templates/build/webpack/config.plugins.js

@@ -79,6 +79,7 @@ const devPlugins = [
  * Plugins used for production builds only
  */
 const prodPlugins = [
+	new webpack.HashedModuleIdsPlugin(),
 	new ImageminPlugin({test: /\.(jpe?g|png|gif|svg)$/i}),
 	configFile.purifyCSS.usePurifyCSS ? new PurifyCSSPlugin(purifyCSSOptions) : false,
 	generateBanners ? new webpack.BannerPlugin({

app/templates/src/handlebars/layouts/_default.hbs

@@ -33,6 +33,9 @@
 	{{{contents}}}
 	<!-- end: content -->
 
+	<!-- webpack runtime JS -->
+	@@runtime.js
+
 	<!-- Vendor JS -->
 	@@vendor.js