Support configuration to automatically remove all files matching a list of paths

[afharo]

I was wondering if we could add a feature where the project would provide a list of paths of files that shouldn't exist in the target branches (such as .github/ISSUE_TEMPLATES).

The typical recommendation is to avoid backporting PRs that have those changes (or manually update the created PR). However, in KIbana we've noticed that the auto-generated .github/CODEOWNERS file tends to be backported more often that we'd like to.

We could solve it separately, just raising the question here in case it makes sense for this tool to remove the listed files in a new config parameter and commit the changes.