To build documentation at GitHub Pages, at the project root path and documentation branch, follow next steps. If gf-pages remote branch exists, remove it.
$ python3 setup.py build_sphinx
$ mkdir .tmp
$ mv docs/build/html/* .tmp
$ git stash
$ git checkout --orphan gh-pages
$ rm -rf *
$ mv .tmp/* .
$ rm -rf .tmp
$ touch .nojekyll
$ git add --all .
$ git commit -m "Project doumentation"
$ git push <remote> gh-pages
$ git checkout <documentation_branch>
$ git branch -D gh-pages
$ git stash pop
Documentation will be available here.