proposal: `keep_files` for specific files only

[iamgio]

Checklist

• I am using the latest version of this action.
• I have read the latest README and followed the instructions.
• I have read the latest GitHub Actions official documentation and learned the basic spec and concepts.

Describe your proposal

This is a niche use-case so feel free to unprioritize or even close if needed.

I'm using Quarkdown as a static site generator (full workflow here).

I'd like to deploy some static files, PDF files in particular, but as opposed to what Hugo can do with the public directory, Quarkdown doesn't support that yet.

Describe the solution you'd like

My proposal is to allow cherry-picking files in the destination dir to keep, so I can manually upload static files to the destination dir without them being deleted at every run of the action.

keep_files: 'static/*'

Describe alternatives you've considered

For now, I'm going to work around with a simple script that copies specific files from the source dir to the destination dir after each build.

Additional context

No response