Support other winding conventions (cw, ccw, spherical, etc.)

[indiejames]

According to the GeoJSON spec (RFC 7946), outer rings of polygons MUST follow the right-hand rule, i.e., be counter-clockwise, whereas the output I see creates polygons with rings that use clockwise winding.

[skjortan23]

Getting the same error this makes the resulting json unusable in later mapbox implementations etc.

[Fil]

This package follows the convention in d3-geo, TopoJSON and ESRI shapefiles, which is (unfortunately) the opposite convention of GeoJSON’s RFC 7946.

[mbostock]

Probably we should support an option that allows the clockwise and containment test to be overridden, or perhaps alternatively, we could enumerate different conventions (e.g., planar-cw, planar-ccw, spherical-cw).