[FR] FirebaseUser.SendEmailVerificationAsync doesn't take in ActionCodeSettings as an argument

### Feature proposal

* Firebase Component: Auth

Currently once you sign-in and get a FirebaseUser, there is a method that triggers email verification `SendEmailVerificationAsync`. However, in other SDK's, there is an option to pass an [ActionCodeSettings](https://firebase.google.com/docs/reference/js/auth.actioncodesettings) object in order to customize the `continueUrl`. However, in the Unity SDK the method does not take any arguments.

This is especially important in the mobile use case, where ideally the user doesn't need to verify their email on the website and then reopen the app after verifying. Additionally this allows us to customize the verification path depending on whether we are on iOS or Android.