chore: document need for frontend model

Author: SychO9

docs/extend/notifications.md

@@ -302,6 +302,12 @@ Open up your index.js (the forum one) and start off by importing your newly crea
 
 Make sure to replace `{nameOfNotification}` with the name of the notification in your PHP blueprint (`getType()`) and replace `{NotificationTemplate}` with the name of the JS notification template we just made! (Make sure it's imported!)
 
+:::tip
+
+If the subject of your notification is a new model, make sure you have a frontend represantation of it registered in the frontend store. [Read more about it here](./models.md#adding-new-models-1)
+
+:::
+
 Let's give users an option to change their settings for your notification. All you have to do is extend the [`notificationGrid`](https://github.com/flarum/framework/blob/main/framework/core/js/src/forum/components/NotificationGrid.js)'s [`notificationTypes()`](https://github.com/flarum/framework/blob/main/framework/core/js/src/forum/components/NotificationGrid.js#L204) function
 
 From [Flarum-Likes](https://github.com/flarum/likes/blob/master/js/src/forum/index.js):