chore: skill for getting started firebaseui iOS

[russellwheatley]

• Getting started skill to help consumers get started with FirebaseUI SwiftUI on iOS.
• Followed skill best practices: agentskills.io/skill-creation/best-practices

[gemini-code-assist]

Code Review

This pull request introduces a new skill definition for setting up FirebaseUI in SwiftUI iOS applications, covering workflows, provider setup, and common pitfalls. The review feedback identifies critical improvements regarding the lifecycle management of the AuthService; specifically, it recommends using @State instead of a let property to ensure state persistence across view updates. Additionally, the feedback suggests providing actionable fixes for Xcode preview failures related to Firebase configuration rather than advising users to ignore them.

[github-actions]

Hello, this PR has been open for more than 28 days with no activity.

If you think this is a mistake, please comment to keep this open. Thanks for contributing!

This PR will be closed in 15 days if no further activity occurs.