Serving docs from a "staging" branch

[cdiggins]

Hi @vim-sroberge, what do you think about us serving the docs from a different branch (e.g. a staging branch). This would allow you to test / demo without merging into main. This would improve allow a PR to be demoed and reviewed properly before going into main. We could even make main automatically push to staging as a github action, so that if main is updated independently, so is the staging branch.