add site to view and upload files

Reviewed-on: sites/file-explorer#4

assets/bootstrap.js

@@ -0,0 +1,5 @@
+import { startStimulusApp } from '@symfony/stimulus-bundle';
+
+const app = startStimulusApp();
+// register any custom, 3rd party controllers here
+// app.register('some_controller_name', SomeImportedController);