make repo-token optional about github-purge-cache-action HOT 1 OPEN

all actions that want to operate on github need a repo token. this can be easily provided with secrets.GITHUB_TOKEN and is generated automatically by the github runner. see https://docs.github.com/en/free-pro-team@latest/actions/reference/authentication-in-a-workflow#about-the-github_token-secret
so the installation is very simple, as no extra token needs to be generated or registered anywhere.

However, I think in the simplest case, we could just read the list of changed files contain in the payload, and not to the diff to the master. this way, the repo token is not needed.

from github-purge-cache-action.