How to leverage GitLab CI/CD for Google Firebase

What this post added

This post details the integration of GitLab CI/CD with Google Firebase for automating application deployments. It covers acquiring a Firebase API key, configuring the `.gitlab-ci.yml` file to install the Firebase CLI, and setting up deployment jobs for Firestore, Firebase Functions, and Firebase Hosting. The post demonstrates how to use the `only` and `changes` keywords in `.gitlab-ci.yml` to trigger deployments for specific infrastructure components based on changes in the repository, and how to secure the Firebase token as a protected and masked CI/CD variable.