Hey thanks for the great work on this library.

I was wondering if it would be possible to get support for checking if a MultiPolygon is within a Polygon.

Would it be sufficient to add another case for MultiPolygon in the switch, and call isPolyInPoly(geom1, geom2) or is it more complex?
https://github.com/Turfjs/turf/blob/master/packages/turf-boolean-within/index.ts#L69