A Python 3 installation is required to build this documentation site. Prepare the environment with:
$ pip3 install -r requirements.txt
If pip points to a Python/pip 3 version you can of course also use that executable.
Then run
$ mkdocs serve
and open http://127.0.0.1:8000 in the browser of your choice.
Note
MkDocs supports hot-reloading changes. However, it does not reload master pages if one of the included pages changes. If you change any document in the includes folder you need to restart MkDocs to see those applied.