Setup Playwright for automating GitHub UI tasks

[sethmlarson]

GitHub doesn't provide APIs for some PSRT features (comments) so we need to use some browser automation (Playwright?) to polyfill this. This is the first time I've used browser automation (I'm more of a Squish / Qt guy, myself) so there'll be plenty of learning to do here.

[sethmlarson]

Since this repository may be moving to be public soon I'm going to start closing some PRs/issues that are no longer necessary (or hopefully won't be if GitHub does deliver new GHSA features).