Extend publish mode to deleting of content

**Is your feature request related to a problem? Please describe.**

Currently, [publish mode](https://www.netlifycms.org/docs/configuration-options/#publish-mode) (Meaning that a PR is created for new content), is not available for deleting content.
This does not fit into our workflow, because we would like to turn on [branch protection](https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/about-protected-branches) in GitHub which means that only PRs can be used to contribute to the main branch, direct pushing is not allowed.
Since deleting content means that the deletion is directly pushed to main, we have a conflict.

**Describe the solution you'd like**

Extend publish mode to deletion of content so that a PR is created when content is deleted instead of a direct push to main.

**Describe alternatives you've considered**

None
**Additional context**

Our environment is hosted by Netlify and we are using GitHub.

cc @duruld