Regression: external contribution CI will fail

[allgreed]

So #109 broke something solved by #54
I've confirmed with @airborn that it only affects CI runs on a PRs from a fork.

Workaround:
Someone with admin powers (likely me) will just verify the contributions manually and override the check requirement should any contributions happen until a fix is issued

Non-starters:
Previous solution is unacceptable as it doubles quadruples the CI execution time.

[airborn]

A possible solution could be to use on: pull_request_target instead of on: pull_request although this has some limitations: https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target