Reorganize and refactor build routine

assets/build/webpack.config.optimize.js

@@ -0,0 +1,26 @@
+'use strict'; // eslint-disable-line
+
+const OptimizeCssAssetsPlugin = require('optimize-css-assets-webpack-plugin');
+const ImageminPlugin = require('imagemin-webpack-plugin').default;
+const imageminMozjpeg = require('imagemin-mozjpeg');
+const cssnano = require('cssnano');
+
+const config = require('./config');
+
+module.exports = {
+  plugins: [
+    new OptimizeCssAssetsPlugin({
+      cssProcessor: cssnano,
+      cssProcessorOptions: { discardComments: { removeAll: true } },
+      canPrint: true,
+    }),
+    new ImageminPlugin({
+      optipng: { optimizationLevel: 7 },
+      gifsicle: { optimizationLevel: 3 },
+      pngquant: { quality: '65-90', speed: 4 },
+      svgo: { removeUnknownsAndDefaults: false, cleanupIDs: false },
+      plugins: [imageminMozjpeg({ quality: 75 })],
+      disable: (config.enabled.watcher),
+    }),
+  ],
+};