This PR migrates off probot and favors GH actions instead.
Caveats:
welcome => we're missing a celebration when folks merge their PRs. I don't think this field is supported by the GH action
triage-new-issues => There is no equivalent. Triaging issues will have to be done manually (if we think it's worth it, we can write our own action for that in a a follow-up PR)
This PR migrates off probot and favors GH actions instead.
Caveats:
Type of change
workflow / dev / contributions