Add an example how to set up a jupyter lab course, demonstrating how participants can activate centrally prepared environments

The current information that is available for using JupyterHub in teaching is quite sparse.

This was the second time we had a bigger Python visualization course using the JupyterHub system (see the workshop repo here).

What was specifically difficult to set up is the creation of a central conda workshop environment that participants (students) enabled in their notebooks when starting the course through the Spawn Link.

I will summarize our experience and submit a merge request, so this can be discussed.