Support simple GeoJSON styling in the map view

[efoley]

It would be nice if GeoJSON rendering in the map view could support simple styling (at least coloring.)

This is easy to implement, but I don't think there is any standardized way of including style in the GeoJSON itself. One way to do this is to pull out feature.properties.color (see example diff here), as this follows the example in the leaflet docs.

Coloring topics (https://github.com/foxglove/studio/issues/3753) would be a partial workaround for this, but it would still be nicer to style from the GeoJSON as that supports more complex cases.