react-map-gl/examples/additional-overlays

As of version 2, the ChoroplethOverlay React component is no longer part of the exported library of react-map-gl.

It has been moved to this examples folder, and applications that still need it can copy it from here instead of importing it directly.

Removing ChoroplethOverlay eliminated a fairly large overlay and a big D3 dependency (in particular, d3-geo) from react-map-gl, which seemed like the right tradeoff since most users are using mapbox styles or deck.gl layers for Choropleths.