add skipAssertUserNotAuthenticated option to signInWithRedirect

[dehli]

Description of changes

This PR allows you to call signInWithRedirect even when a user is already signed in. The use-case is that we have Google login and some customers want to enforce that their users only sign-in with Google. If a user logs in with their password we will show an error along with a button prompting them to sign-in via Google. With v5, you could call Auth.federatedSignIn even when a user was already logged in. This allows you to similarly call signInWithRedirect.

I'm 50/50 on the name, might want to do the inverse so a truthy value would allow you to skip the assertion.
Edit: Decided to do the inverse instead.

Description of how you validated changes

Used patch-package with these changes.

Checklist

• PR description included
• yarn test passes
  • I'm getting 4 failures that are unrelated to my changes.
• Tests are changed or added
  • Added placeholders for the time being since the function itself only has placeholders. Figured I'd submit the PR without them first.
• Relevant documentation is changed or added (and PR referenced)
  • Is adding comments to interface all that's needed?

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[cwomack]

Hey, @dehli 👋. We appreciate you opening this PR and will review it internally and reach out if there's further questions or suggestions.