Workflows triggered by events, not only on time.

[aafvstam]

I wanted to create a documentation workflow that was triggered by Merges/PRs/etc. (events) But run into the restriction that it can only be done by Actions, and not in the GHCP App. The downside of Actions is that they are repo-related. In my example, I want to maintain a separate Documentation Repo that collects/creates documentation from multiple repos.