Add support for Multipoint geometry objects

[mvanbommel]

Currently, multipoint geometry objects are not supported in the app. Addressing this issue will involve identifying when a data set uses mutlipoints, and appropriately plotting those multipoints on the map.

Contrived example data: https://developer.here.com/documentation/studio/map_customization_suite_hlp/dev_guide/topics/geojson-basics.html

If you know of a real dataset that uses multipoints, please add it in the comments.

[mvanbommel]

Actual data example: https://hub.arcgis.com/datasets/IowaDOT::project-scheduling-public-bid-multipoint?layer=0