Added custom button editor

Added the long planned button editor. This solution does not look optimal, but works... mostly.

This solution is implemented with JavaScript and the current versions code is very unorganized mostly uncommented and the HTML is still mostly done with inline code. I hope I will fix this in future revisions.

To learn more about the new button editor, read:
https://littlelink-custom.com/blog/upcoming-features/
https://littlelink-custom.com/blog/progress-of-the-new-button-editor/

Author: JulianPrieber

app/Http/Controllers/UserController.php

@@ -328,4 +328,4 @@ public function editProfile(request $request)
         }
         return back();
     }
-}
+}