What's the purpose of .firebase/hosting. ALPHANUM.cache
Solution 1:
This file is part of a new feature in Firebase Hosting that minimizes the size the time of a hosting deployment by only uploading the files that changed since the last deployment. It's new in CLI version 4.2.0, and you can read about that on GitHub.
As Frank suggested, you should definitely add the .firebase directory to your .gitignore or equivalent file, since it contains information that's not strictly part of your project, and is likely not applicable for everyone sharing and contributing to your project source code.