Make stream_chat_persistence a add on dependency instead of shipping it with the llc

Signed-off-by: Sahil Kumar <[email protected]>

packages/flutter_widgets/example/lib/routes/routes.dart

@@ -1,5 +1,6 @@
 /// Define all the route names here
 class Routes {
+  static const String APP = '/app';
   static const String HOME = '/home';
   static const String CHOOSE_USER = '/choose_user';
   static const String ADVANCED_OPTIONS = '/advance_options';