Support event arrays

[sfmig]

Is your feature request related to a problem? Please describe.
We discussed it could be very useful to have event arrays added to a movement dataset. These arrays would have an extra dimension to represent the event tag, which could be "animal inside ROI 1", or "U-turn".

We could then support computation of basic stats (mean, median, std) for periods between events, plot ethograms for a specific tag, etc

Additional context
Users may want to analyse the event arrays alognside neural recordings, so maybe we want to keep pynapple in mind? I am not very familiar with this though.