Configure dependabot
Configure dependabot

By using a configuration file here it is easier to comment on and keep
track of our preferences. Plus we have more power to ignore specific
dependencies this way across version bumps, which the chat UI doesn't
allow us to do.

dartajax/frontend,thecoolestguy/frontend,thecoolestguy/frontend,dartajax/frontend,ilios/frontend,jrjohnson/frontend,jrjohnson/frontend,ilios/frontend