Add terser minifier for webpack

Makefile

@@ -19,7 +19,6 @@ SASS			?= ./node_modules/.bin/node-sass
 SED				?= sed
 SPHINXBUILD	 	?= ./bin/sphinx-build
 SPHINXOPTS		=
-UGLIFYJS		?= node_modules/.bin/uglifyjs
 XGETTEXT		= xgettext
 
 

package.json

@@ -101,8 +101,7 @@
     "sinon": "^8.1.1",
     "sizzle": "^2.3.4",
     "style-loader": "^0.23.1",
-    "uglify-es": "^3.3.9",
-    "uglify-js": "^3.7.4",
+    "terser-webpack-plugin": "^2.3.4",
     "urijs": "^1.19.1",
     "webpack": "^4.35.3",
     "webpack-cli": "^3.3.5",

webpack.common.js

 /* global __dirname, module */
 const path = require('path');
+const TerserPlugin = require('terser-webpack-plugin');
 
 bootstrap_ignore_modules = ['carousel', 'scrollspy'];
 
@@ -16,6 +17,10 @@ module.exports = {
     externals: [{
         "window": "window"
     }],
+    optimization: {
+        minimize: true,
+        minimizer: [new TerserPlugin()]
+    },
     watchOptions: {
         ignored: [/dist/, /spec/, /.*\~/]
     },

webpack.dev.js

@@ -11,9 +11,6 @@ module.exports = merge(prod, {
         publicPath: ASSET_PATH,
         filename: 'converse.js',
     },
-    optimization: {
-        minimize: false,
-    },
     devtool: 'source-map',
     plugins: [
         new MiniCssExtractPlugin({filename: '../dist/converse.css'}),