Type annotation incomplete for visx/geo fitExtent/fitSize

[aendra-rininsland]

These lines for the fitExtent and fitSize props have ExtendedFeatureCollection commented out for some reason, which is preventing me from passing a FeatureCollection to my Projection component in TypeScript.

https://github.com/airbnb/visx/blob/master/packages/visx-geo/src/projections/Projection.tsx#L71
https://github.com/airbnb/visx/blob/master/packages/visx-geo/src/projections/Projection.tsx#L76

AFAICT it works fine to pass a FeatureCollection to; I'd submit a PR fixing those lines but given they're commented out was thinking there might be another reason why that I'm missing.