Test example notebooks in CI

[CasperWA]

The example should be run at a part of the CI testing.

This repository already has an end-2-end test that does exactly this. No need to also run the tutorial.
That said, the mkdocs-jupyter plugin allows for executing the notebooks upon building the documentation, hence this could act as a CI test for whether the notebook works or not.
However, since a separate server is required and the notebook references localhost:80 it might be quite tricky to make it work properly. Hence, I'd consider it out-of-scope for this PR and writing this example, but definitely worth further investigation down the road.

Originally posted by @CasperWA in #125 (comment)

Notebooks:

• otelib.ipynb
• dlite.ipynb

Update: PR #127 which introduced the dlite.ipynb also added execution test for it when building the documentation.