Add a test for template code snippets to CI

The contribution guide specifies, that there should be an example given after a code snippet that contains a template. Check that via CI! E. g. https://doc.zih.tu-dresden.de/access/jupyterhub/ contains: conda create --prefix /home/<USER>/user-kernel/my-kernel python=3.6 without any example.

mentioned in issue #9 (closed)

added CI/CD Pipeline label

assigned to @s2817051--tu-dresden.de

mentioned in merge request !481 (merged)

changed milestone to %Meeting-2022-02-23

mentioned in commit 71f6a13f

closed with merge request !481 (merged)