Setup Netlify Automated PR Review Instances/Environments

[ElijahLynn]

As a developer I want to see and test my code changes before they get merged so that I can get feedback on them as rapidly as possible and avoid breaking the site.

https://www.netlify.com/blog/2016/07/20/introducing-deploy-previews-in-netlify/

AC:

• Stakeholders can see and approve changes in context before they are deployed to production.
• Technically: Full-site preview is posted as a link on the PR after pushing changes to my PR.

[ElijahLynn]

This is working now in #25, e.g. https://deploy-preview-25--agile6.netlify.com. All PRs will get a comment with a link to the new commit pushed to a PR. This was already happening on every PR but lacking the visibility with a comment.

#25 (comment)