Move symfony stuff to own folder

symfony/assets/app.js

@@ -0,0 +1,10 @@
+import './bootstrap.js';
+/*
+ * Welcome to your app's main JavaScript file!
+ *
+ * This file will be included onto the page via the importmap() Twig function,
+ * which should already be in your base.html.twig.
+ */
+import './styles/app.css';
+
+console.log('This log comes from assets/app.js - welcome to AssetMapper! 🎉');