CI pipeline

This merge request resolves Issue #5

Added CI pipeline testing all notebook tutorials except the output-function tutorial.

Note that the tests do not test all aspects of the tutorials. Generally, they test that the notebooks complete successfully (without generating any errors) and that output files are created as expected. The contents of the output files are NOT inspected.

Note: I was unable to create a test for the output-function tutorial because this tutorial actually is supposed to trigger an error! (Suggestion: could the tutorial be modified so no errors are thrown? This would allow us to include it in the test suite following the same approach as for the other tests.)