[FEATURE] Switch to Terser for JavaScript minification

`uglify-es` is no longer maintained:
mishoo/UglifyJS#3156 (comment)

Terser is a maintained fork of uglify-es, which is used by most of the
existing bundling tools.

lib/lbt/bundle/AutoSplitter.js

@@ -1,6 +1,6 @@
 "use strict";
 
-const uglify = require("uglify-es");
+const terser = require("terser");
 const {pd} = require("pretty-data");
 
 const ModuleName = require("../utils/ModuleName");
@@ -199,7 +199,7 @@ class AutoSplitter {
 				let fileContent = await resource.buffer();
 				if ( this.optimize ) {
 					// console.log("uglify %s start", module);
-					const result = uglify.minify({
+					const result = terser.minify({
 						[resource.name]: String(fileContent)
 					}, {
 						warnings: false, // TODO configure?

lib/lbt/bundle/Builder.js

@@ -2,7 +2,7 @@
 // for consistency of write calls, we generally allow template literals
 "use strict";
 
-const uglify = require("uglify-es");
+const terser = require("terser");
 const {pd} = require("pretty-data");
 const esprima = require("esprima");
 const escodegen = require("escodegen");
@@ -323,7 +323,7 @@ class BundleBuilder {
 
 	compressJS(fileContent, resource) {
 		if ( this.optimize ) {
-			const result = uglify.minify({
+			const result = terser.minify({
 				[resource.name]: String(fileContent)
 			}, {
 				warnings: false, // TODO configure?

lib/processors/uglifier.js

@@ -1,4 +1,4 @@
-const uglify = require("uglify-es");
+const terser = require("terser");
 const copyrightCommentsPattern = /copyright|\(c\)(?:[0-9]+|\s+[0-9A-za-z])|released under|license|\u00a9/i;
 
 /**
@@ -13,7 +13,7 @@ const copyrightCommentsPattern = /copyright|\(c\)(?:[0-9]+|\s+[0-9A-za-z])|relea
 module.exports = function({resources}) {
 	return Promise.all(resources.map((resource) => {
 		return resource.getString().then((code) => {
-			const result = uglify.minify({
+			const result = terser.minify({
 				[resource.getPath()]: code
 			}, {
 				warnings: false,

package.json

@@ -116,7 +116,7 @@
 		"rimraf": "^2.6.3",
 		"semver": "^6.3.0",
 		"slash": "^3.0.0",
-		"uglify-es": "^3.2.2",
+		"terser": "^4.1.2",
 		"xml2js": "^0.4.17",
 		"yazl": "^2.5.1"
 	},

test/lib/lbt/bundle/AutoSplitter.js

@@ -1,6 +1,6 @@
 const test = require("ava");
 const sinon = require("sinon");
-const uglify = require("uglify-es");
+const terser = require("terser");
 const {pd} = require("pretty-data");
 const BundleResolver = require("../../../../lib/lbt/bundle/Resolver");
 const AutoSplitter = require("../../../../lib/lbt/bundle/AutoSplitter");
@@ -178,7 +178,7 @@ test("_calcMinSize: js resource", async (t) => {
 
 
 test.serial("_calcMinSize: uglify js resource", async (t) => {
-	const stubUglify = sinon.stub(uglify, "minify").returns({code: "123"});
+	const stubTerser = sinon.stub(terser, "minify").returns({code: "123"});
 	const pool = {
 		findResourceWithInfo: function() {
 			return {
@@ -194,7 +194,7 @@ test.serial("_calcMinSize: uglify js resource", async (t) => {
 	const autpSplitter = new AutoSplitter(pool);
 	autpSplitter.optimize = true;
 	t.deepEqual(await autpSplitter._calcMinSize("mymodule.js"), 3);
-	stubUglify.restore();
+	stubTerser.restore();
 });
 
 test("_calcMinSize: properties resource", async (t) => {