Add more robust intersection checking, inc for end of segments

[rowanwins]

This PR

• Uses robust-predicates for an initial check for intersection
• Adds a special check for intersections of end segments that don't belong to the same contour

[smallsaucepan]

Hi @rowanwins do you think this could solve the problem we're seeing here - Turfjs/turf#2667?

[rowanwins]

Hi @smallsaucepan

I've just run some tests usig the turfjs issue and have made some additional modifications, TBH I'm not sure why I never thought of checking endpoints touching 😂
Anyway this should now be resolved in this branch.
I think I'll release as a new major version.

[smallsaucepan]

Brilliant. Thanks @rowanwins