Make build output ascii-only to resolve invalid regex issue

Something changed in MediaWiki so that its parser/sanitizer now does some sort of pre-save transform mangling some unicode characters – resulting in `Uncaught SyntaxError: invalid range in character class error.`

This makes the terser minifier avoid emitting unicode characters in output (they would be escaped).

Author: siddharthvp

Gruntfile.js

@@ -76,6 +76,7 @@ module.exports = function (grunt) {
 					minimizer: [
 						new TerserPlugin({
 							extractComments: /@preserve/,
+							terserOptions: { output: { ascii_only: true } }
 						}),
 					],
 				},