Add allow-list for PR author

[schlessera]

Feature Request

In order to avoid this workflow from being abused by external PRs, it would be great to have an allow-list of PR authors that needs to match. This could be a comma-separated list like so:

with:
   author: schlessera,github-bot

If such a list is provided, PRs authored by a GitHub user would not be considered.

[core23]

The original idea of this action was to merge PRs with a specific label.

The labeling strategy is an other problem that is out of scope. You should now when to apply labels.

If you provide a PR, I would accept it.