🐛 Firebase messaging pass along action identifier to iOS

## What feature would you like to see?

A way to determine with action identifier was used when receiving a notification.

I am able to setup categories on iOS and I can send a notification with a category id from Firebase Messaging. But when I tap on one of my actions, I do not see a way to get the action id in Flutter. I am able to get the category id of the notification, but not the action.
