Handle rate limiting gracefully

When testing to make sure nothing breaks, I semi-often get rate-limited by GitHub. This is because there are (IIRC) 50 queries accepted before 1-hour rate limiting kicks in.

Obviously this shouldn't be happening for a normal user (though I'd applaud a user that was working on dozens of good-first-issues), but it may happen for contributors.

Checklist:
- [ ] Handle errors in the CLI gracefully
- [ ] Allow consumers of the module to pass GitHub authentication, which we would then pass to @octokit/rest
- [ ] Documentation for both of the above