Make `Reviewer` model?

[sneakers-the-rat]

Opening this as a question - working on making badges right now, and reading the minutes from the meeting today (sorry i just never know when these are!), I am wondering if we want to make a Reviewer model?

It makes sense to exist semantically, since Reviewers exist! We could start with just having the single field of the gh username and appropriate relations to the other person models because a person can be a reviewer and an editor and an author, and then iterate on that as needed :)

Would be happy to draft this.