Build: add GitHub Actions workflow to update Filestash

[timmywil]

Summary

3.x companion of https://github.com/jquery/jquery/pull/5434

Replaces the jenkins workflow to update git versions of jQuery on the Filestash server. The filestash environment is already set up in the jQuery repo settings and includes the necessary SSH private key and filestash server URL.

Here's a sample of the 3.x workflow running as a dry run: https://github.com/timmywil/jquery/actions/runs/8205774067/job/22443405621

We should disable the jenkins workflow before merging.

Checklist

• [x] New tests have been added to show the fix or feature works
• [x] If needed, a docs issue/PR was created at https://github.com/jquery/api.jquery.com

[timmywil]

Files updated on the CDN as expected.