Update Webpack front-end packages

Beyond bumping all of the package versions up, this also replaces
UglifyJS with Terser to minify the JS files in production.

assets/package.json

@@ -1,30 +1,30 @@
 {
   "repository": {},
   "dependencies": {
-    "jquery": "~3.4.1",
-    "@fortawesome/fontawesome-free": "~5.12.0",
-    "bootstrap": "~4.4.1",
-    "popper.js": "~1.16.0"
+    "jquery": "~3.5.1",
+    "@fortawesome/fontawesome-free": "~5.14.0",
+    "bootstrap": "~4.5.0",
+    "popper.js": "~1.16.1"
   },
   "devDependencies": {
-    "@babel/core": "~7.7.7",
-    "@babel/preset-env": "~7.7.7",
-    "@babel/register": "~7.7.7",
-    "autoprefixer": "~9.7.3",
-    "babel-loader": "~8.0.6",
-    "copy-webpack-plugin": "~5.1.1",
-    "css-loader": "~3.4.0",
-    "file-loader": "~5.0.2",
+    "@babel/core": "~7.11.0",
+    "@babel/preset-env": "~7.11.0",
+    "@babel/register": "~7.10.5",
+    "autoprefixer": "~9.8.6",
+    "babel-loader": "~8.1.0",
+    "copy-webpack-plugin": "~6.0.3",
+    "css-loader": "~4.2.0",
+    "file-loader": "~6.0.0",
     "mini-css-extract-plugin": "~0.9.0",
-    "node-sass": "~4.13.0",
+    "node-sass": "~4.14.1",
     "optimize-css-assets-webpack-plugin": "~5.0.3",
     "postcss-loader": "~3.0.0",
     "precss": "~4.0.0",
-    "sass-loader": "~8.0.0",
-    "uglifyjs-webpack-plugin": "~2.2.0",
-    "webpack": "~4.41.5",
-    "webpack-cli": "~3.3.10",
-    "webpack-merge": "~4.2.2"
+    "sass-loader": "~9.0.2",
+    "terser-webpack-plugin": "~3.1.0",
+    "webpack": "~4.44.1",
+    "webpack-cli": "~3.3.12",
+    "webpack-merge": "~5.1.1"
   },
   "scripts": {
     "build": "/node_modules/webpack/bin/webpack.js --mode=production -p",

assets/webpack.config.js

@@ -1,9 +1,9 @@
-var merge = require('webpack-merge');
+var { merge } = require('webpack-merge');
 var webpack = require('webpack');
 var CopyWebpackPlugin = require('copy-webpack-plugin');
 var MiniCssExtractPlugin = require('mini-css-extract-plugin');
 var OptimizeCSSAssetsPlugin = require('optimize-css-assets-webpack-plugin');
-var UglifyJsPlugin = require('uglifyjs-webpack-plugin');
+var TerserPlugin = require('terser-webpack-plugin');
 
 var common = {
   watchOptions: {
@@ -46,7 +46,7 @@ var common = {
   },
   optimization: {
     minimizer: [
-      new UglifyJsPlugin({cache: true, parallel: true}),
+      new TerserPlugin({cache: true, parallel: true, sourceMap: false}),
       new OptimizeCSSAssetsPlugin({})
     ]
   }
@@ -69,7 +69,7 @@ module.exports = [
       ]
     },
     plugins: [
-      new CopyWebpackPlugin([{from: __dirname + '/static'}]),
+      new CopyWebpackPlugin({patterns: [{from: __dirname + '/static'}]}),
       new MiniCssExtractPlugin({filename: 'css/app.css'}),
       new webpack.ProvidePlugin({$: 'jquery', jQuery: 'jquery'}),
     ]