Add terms and conditions to Firebase UI Auth

[pierpo]

On the other frameworks SDKs (Java, web, Swift...) we can add a terms and conditions to the Firebase authentication UI. I could not find such a feature in the Flutter SDK.

I guess it would make sense to add it to match the other SDKs' features. 😊

Example here:

https://firebase.google.com/docs/auth/android/firebaseui

[pierpo]

Sorry, this is a duplicate. I had searched in the issues and not the discussions.

#10729