Archive git.torproject.org/project/web/styleguide and migrate to gitlab

As of today, the static-shim CI job is working for this repository and can deploy to production. We no longer need Jenkins for this repo, and can move off of git.tpo entirely.

Shortly, I'll be disabling the Jenkins job and archiving the git.tpo repository. This gitlab repo should be the new canonical source for styleguide.tpo