Update the site scanning documentation repo

This issue can serve as a running list of small changes to make to the documentation repo.

[ ] Add in reference to alpha status
[x] expand team workflows
[ ] add links to slide decks
[ ] Look through old files to see what we still need to keep
[ ] Add relevant policy hooks that support or involve this program (or are indirectly impacted by it)
[ ] Create a data validation checklist (notes), and possibly link off to a google sheet of it
[ ] style guide, e.g. Federal or federal (linking off to 18F's)

18F / site-scanning