Use a new MkDocs site

.gitlab-ci.yml

README.md

docs/CNAME

docs/about/contributing.md

docs/about/license.md

docs/about/release-notes.md

docs/css/extra.css

docs/img/initial-layout.png

docs/img/mkdocs.png

docs/img/multipage.png

docs/img/readthedocs.png

docs/img/screenshot.png

docs/img/search.png

docs/img/site-name.png

docs/img/win-py-install.png

docs/index.md

docs/user-guide/configuration.md

docs/user-guide/custom-themes.md

docs/user-guide/deploying-your-docs.md

docs/user-guide/styling-your-docs.md