rm: cannot remove 'README.md': Permission denied

Hi!
I tried to do something similar to prevent self-hosted runners from filling up the filesystem and came across your action.

If I use the action I am getting a permission denied error on trying to remove the files. Apparently the docker run does not have sufficient access to the _work dir.
Can this be fixed somehow?

Action log from my workflow:

rm: cannot remove 'Dockerfile': Permission denied
rm: cannot remove 'README.md': Permission denied

Proposal:
Add a cleanup.sh to the image with the rm -rf command and call the cleanup.sh in the action.yml via run.post-entrypoint: '/cleanup.sh'. This ensures that the cleanup task is always run after the workflow is done, wether it fails or not.