Branch protection on the main branch

[maxwofford]

Currently we don't have branch protection warning users they're merging in a change that breaks the build. I'd like to add branch protection to the main branch preventing merge unless CI passes. This wouldn't actually slow down development because merging into main (currently) just fails silently and leaves production on the previous commit. Branch protection can be overwritten, but requires an extra prompt to ensure the user knows they're merging in something that will fail to deploy.

[maxwofford]

Once #234 is merged this would be good to add. Unfortunately this is just a repo setting, not a PR change. @leomcelroy, mind if I edit this in the settings?

[leomcelroy]

Go for it!