Docs don't explain critical step for using github-ci

[dream-dasher]

The following is in the web.yml generated for github-ci, but it is not in the hosting documentation.

      # Note that once the gh-pages branch exists, you must
      # go into repo's settings > pages and set "deploy from branch: gh-pages".
      # The other defaults work fine.

Given the goal of this tool, make creating a repo site simple, calling out this arcane to many step would likely help quite a few people use your tool.