17: Introduce Grunt based minification of JS and CSS (#686)

* Introduce Grunt based minification of JS and CSS

* Update package versions to latest, update config

* Update minified files

* Add missing comma

* Add jshint hints for Gruntfile.js

* Remove incompatible esversion

* Fix JSHint issues by using old syntax for now

Co-authored-by: Dominik Schilling <dominikschilling+git@gmail.com>

.gitignore

@@ -3,3 +3,6 @@
 # Composer
 composer.lock
 /vendor/
+
+npm-debug.log
+node_modules

Gruntfile.js

@@ -0,0 +1,52 @@
+/* jshint node:true */
+module.exports = function( grunt ) {
+	var WORKING_DIR = '.';
+
+	require( 'load-grunt-tasks' )( grunt );
+
+	grunt.initConfig( {
+		uglify: {
+			options: {
+				output: {
+					ascii_only: true
+				}
+			},
+			core: {
+				expand: true,
+				cwd: WORKING_DIR,
+				dest: WORKING_DIR,
+				src: [
+					'assets/js/**/*.js',
+
+					// Exceptions.
+					'!**/*.min.js'
+				],
+
+				// Custom rename function to support files with multiple dots.
+				rename: function( dst, src ) {
+					return src.replace( '.js', '.min.js' );
+				}
+			}
+		},
+		cssmin: {
+			core: {
+				expand: true,
+				cwd: WORKING_DIR,
+				dest: WORKING_DIR,
+				src: [
+					'assets/css/*.css',
+
+					// Exceptions.
+					'!**/*.min.css'
+				],
+
+				// Custom rename function to support files with multiple dots.
+				rename: function( dst, src ) {
+					return src.replace( '.css', '.min.css' );
+				}
+			}
+		}
+	} );
+
+	grunt.registerTask( 'default', [ 'uglify', 'cssmin' ] );
+};