Automatically deploy documentation

It is desirable to automatically deploy documentation to e.g. readthedocs or gitlab pages (see #35 (closed) for a discussion on man pages).

Gitlab's rendering capabilities for rst are unfortunately subpar which makes using it in the context of "in code documentation" very painful...

My suggestion would therefore be: Switch all in-code documentation to use markdown, but use restructuredtext for user-facing documentation (unless there are good reasons to use markdown there as well).