domain/user_notification_vo library

1. rdev_riverpod_firebase_user_notification package
2. documentation
3. domain/user_notification_vo.dart

rdev_riverpod_firebase_user_notification package

1. Libraries
2. application/user_notifications_data_service
3. application/user_notifications_service
4. data/user_notifications_repository
5. domain/user_notification_model
6. domain/user_notification_vo