Auto request review for backports #534
Description
Is your feature request related to a problem? Please describe.
Sometimes, authors forget about their backports and they go stale. While it's possible to add the author as assignee, there are still cases that slip through. Developers may have set up ways to be reminded of requested reviews, but not of being assigned to a PR.
Describe the solution you'd like
Add a new input add_reviewers (space or comma delimited list of usernames) that allows specifying the users to request a review from.
Usage to assign the original author depends on the event that triggered the workflow.
Describe alternatives you've considered
Alternatively, add a new input to request a review from the original author add_author_as_reviewer (boolean). This is less flexible that the other solution, although perhaps easier to use for the most common case. We can also support both options.