Add configuration for PurgeCSS

resources/assets/build/webpack.config.optimize.js

-'use strict'; // eslint-disable-line
+'use strict' // eslint-disable-line
 
-const { default: ImageminPlugin } = require('imagemin-webpack-plugin');
+const {default: ImageminPlugin} = require('imagemin-webpack-plugin');
 const imageminMozjpeg = require('imagemin-mozjpeg');
 const UglifyJsPlugin = require('uglifyjs-webpack-plugin');
+const glob = require('glob-all');
+const PurgecssPlugin = require('purgecss-webpack-plugin');
 
-const config = require('./config');
+const config = require('./config')
 
 module.exports = {
   plugins: [
     new ImageminPlugin({
-      optipng: { optimizationLevel: 2 },
-      gifsicle: { optimizationLevel: 3 },
-      pngquant: { quality: '65-90', speed: 4 },
+      optipng: {optimizationLevel: 2},
+      gifsicle: {optimizationLevel: 3},
+      pngquant: {quality: '65-90', speed: 4},
       svgo: {
         plugins: [
-          { removeUnknownsAndDefaults: false },
-          { cleanupIDs: false },
-          { removeViewBox: false },
+          {removeUnknownsAndDefaults: false},
+          {cleanupIDs: false},
+          {removeViewBox: false},
         ],
       },
-      plugins: [imageminMozjpeg({ quality: 75 })],
+      plugins: [imageminMozjpeg({quality: 75})],
       disable: (config.enabled.watcher),
     }),
     new UglifyJsPlugin({
@@ -31,5 +33,16 @@ module.exports = {
         },
       },
     }),
+    new PurgecssPlugin({
+      paths: glob.sync([
+        'app/**/*.php',
+        'resources/views/**/*.php',
+        'resources/assets/scripts/**/*.js',
+        'vendor/mwdelaney/sage-bootstrap4-navwalker/*.php',
+      ]),
+      safelist: [
+        'hr',
+      ],
+    }),
   ],
-};
+}