Mkdocs and Actions to publish it on GitHub Pages

[Jetman80]

• added pages.yml to publish pages
• added mkdocs.yml, requirements_mkdocs.txt to build mkdocs
• Mike produces verstions and uses mkdocs
• versions are being stored in gh-pages branch
• mkdocs uses material theme, jypiter, docstrings plugins
• .pages desctibes navigation

[root-11]

Call me in the morning and let's run through the code & github settings.