Use proper arguments to apply labels from original PR to backport PR.
Improve target branch detection.
Co-authored-by: AbsurdlyLongUsername <22662897+absurdlylongusername@users.noreply.github.com>
The workflow can be triggered by creating a comment on a closed PR: /backport <TARGET_BRANCH>
The backport can only be triggered by people with write access to the repository.