Add terser as minifier.

webpack.config.js

@@ -2,7 +2,7 @@ const Webpack = require("webpack");
 const MiniCssExtractPlugin = require("mini-css-extract-plugin");
 const { CleanWebpackPlugin } = require("clean-webpack-plugin");
 const HtmlWebpackPlugin = require("html-webpack-plugin");
-const UglifyJsPlugin = require("uglifyjs-webpack-plugin");
+const TerserPlugin = require("terser-webpack-plugin");
 
 const path = require("path");
 
@@ -78,9 +78,10 @@ module.exports = (env, { mode }) => ({
       name: "vendor",
       minChunks: 2,
     },
+    minimize: true,
     minimizer: [
-      new UglifyJsPlugin({
-        sourceMap: true,
+      new TerserPlugin({
+        parallel: true,
       }),
     ],
   },