Add bounding boxes example

[sfmig]

Is your feature request related to a problem? Please describe.
Since movement is expanding to include bounding boxes in its analyses, we could add an example for a bounding boxes case.

Describe the solution you'd like
An example similar to the Load and explore pose tracks example, for bounding boxes.

Describe alternatives you've considered
We could have it in the same notebook as the pose tracks but that feels a bit unnecessarily cramped.

Additional context
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