Add to contributors in the current PR

**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 :-(