Update community contributions sheet action

[MisRob]

Summary

Updates the action that updates the community contributions spreadsheet:

• (1) Removes information about when a PR was updated in favor of its creation date (that's what I need most, I don't use updated date) API reference
• (2) Attempts to make the action run not only when called from other repositories, but also from this .github repository (since we receive community contributions here regularly as well)

Reviewer guidance

I'd particularly appreciate feedback on (2) fc03eb0 - I hope it's that simple but am rather uncertain.

[rtibbles]

Changes make sense, I have made the secrets that this workflow uses available to this repository (where they weren't already) so hopefully this should also run locally.

[MisRob]

Ah I didn't realize that, thank you. I will observe how it works :)