Add to contributors in the current PR

[flanakin]

Is your feature request related to a problem? Please describe.
There are times when someone starts a PR, but never finishes it. In those cases, I want to add them upfront so I don't forget later, but I don't want to commit a second PR when their contribution isn't complete.

Describe the solution you'd like
Add a commit to the current PR rather than creating a new PR.

Describe alternatives you've considered
Manually add them :-(

[lwasser]

Oh this is an interesting request. I can see the use case. What I think will be hard is that it would set you up for merge conflicts on other pr's or on that pr if you add other contributors in the meantime. and then you'd have to weed through JSON to resolve the conflict. I'm going to flag this as an feature issue for us to think about.