Add notebook rendering to docs

[raar1]

This adds notebook rendering to the documentation page under an Examples heading. I found errors in the existing Griftpark notebooks so I didn't add them for now. All the Amersfoort notebooks should be there and seem to render ok.

Note that it is not possible to render notebooks from examples/ directly in a portable fashion (see MiBiPreT/mibitrans#141) so currently there is a separate /docs/examples directory that you must copy notebooks to if you want them to be included in the docs. In future there may be a better solution. If it's really annoying, we could think about a script to automatically copy notebooks over, but this is likely to confuse people so deliberately and explicitly choosing to copy certain notebooks still seems like a better option.

You can test the rendering locally by running pip install .[doc] to get the new docs dependencies down, and then mkdocs serve

Fixes #127

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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[JaroCamphuijsen]

This looks good! Can you maybe add a distinction between the "ordination" notebooks in the original example folder already. Currently they get rendered with exactly the same title in the documentation, which makes it confusing.