Advertise CI artifacts better

[effigies]

We now have a bot that will automatically find the rendered docs in the CircleCI artifacts and create a link in the CI checks at bottom. This could be a bit more flashy or better advertised. A couple options include (in rough order of difficulty):

1. Add language to the PR template letting people know to look there. Possibly CONTRIBUTING.md as well.
2. Switch to Netlify as shown in [WIP] Restructure Testing chapter the-turing-way/the-turing-way#613, which seems to perform various checks, render, and make the first comment on a PR. It also edits the comment, rather than re-commenting, keeping an up-to-date rendering at the top of the thread while not overly polluting the comment thread.
3. Fiddle with the bot to do some of the nice things Netlify does

Follow-up to #315, please refer to discussion there for anything I may have missed.