Add PR previews

[nimbinatus]

Description of the requested feature

After the site moves to a static site generator as noted in #380, add a preview comment, similar to Netlify site previews, to any open PR to allow the user to validate updates are present.

(Suggestion: https://github.com/rossjrw/pr-preview-action, as noted in #381 )

Related issues

• feat(zola): move site to Zola #381 - The preview is currently giving me trouble, so it will be addressed in a future PR.
• Move site to static site generator #380