Add gaitmap example

[JuliusWelzel]

Provide an example for foot worn IMUs using gaitmap with importing into NGMTRecording and exporting events from NGMT

[JuliusWelzel]

I added an example using the KeepControl data here: https://github.com/neurogeriatricskiel/KielMAT/blob/example_gaitmap/examples/basic_03_foot_imus.ipynb

@rmndrs89 Could you check if you like the overall structure, then I would add some text. Also I am not sure if the comparison is useful, left_foot vs. lower back and I am not sure if Gaitmap returns ICDs. Feel free to comment or edit.

[JuliusWelzel]

@hansencl mentioned we should also compare it to the optical MoCap data to check the results and compare to ground truth.

[rmndrs89]

Please check: https://gaitmap.readthedocs.io/en/latest/auto_examples/event_detection/herzer_event_detection.html#sphx-glr-auto-examples-event-detection-herzer-event-detection-py