Add admin client JS/LESS to extension stub

stubs/extension/js/forum/Gulpfile.js

@@ -1,5 +1,7 @@
 var gulp = require('flarum-gulp');
 
 gulp({
-  modulePrefix: '{{name}}'
+  modules: {
+    '{{name}}': 'src/**/*.js'
+  }
 });

stubs/extension/js/forum/src/main.js

@@ -1,6 +1,6 @@
 import { extend } from 'flarum/extend';
 import app from 'flarum/app';
 
-app.initializers.add('{{name}}', app => {
+app.initializers.add('{{name}}', () => {
   // TODO
 });