Pie/ bar charts for map_summary

[martijn-bollen]

I would extend map_summary such that it allows for visualizing species composition, age composition, sex composition, etc. (essentially any ordinal/categroical grouping variable from summarize_observations) more intuitively.

One way to do this is to implement leaflet.minicharts::addMinicharts() (see vignette) type of bar/ pie plots. Note addMinicharts does not support leaflet's native clustering upon zooming in/out, which is something that should be implemented here.

[damianooldoni]

Thanks @martijn-bollen. I would be an interesting addition. Sure to be tackled after the release of version 1.0.