Set up some sort of Pull Request preview

[pganssle]

Right now if someone makes a PR, I'd have to pull their code and then build it myself. Ideally I'd have some sort of CI that would let me click a link and see what the github pages is going to look like after the PR is merged.

I think there's a way to do it with netlify, and I vaguely remember some complicated and annoying way to do it directly within GH.

Possibly useful links:

• https://github.com/orgs/community/discussions/7730
• https://github.com/actions/deploy-pages/blob/368bf1aa22b9265440e251b9216520e3f91c2d5b/action.yml#L36-L39
• https://github.com/rossjrw/pr-preview-action