Return more information

[rowanwins]

This branch explores returning some extra information for intersection points.

• distance of intersection along segments (using a planar distance calc)
• segment index of the segments

As it currently stands this would be a breaking change, although I could possibly expose the info via an option.

[hanneshdc]

Hey @rowanwins - I'd be really interested in this change. Returning the vertex ID would allow me to fix a common bug in the turf geospatial library's line split function: Turfjs/turf#1232

Currently that function relies on a buggy point-to-line search to find the vertex IDs, when it could be returned from this package instead.

I'm not a big fan of options changing the return type of a function, so instead consider a seperate function. I'd suggest the following API:

const sweepLine = require('sweepline-intersections');
// normal way:
const results1 = sweepLine(fc); // returns [number, number][]

// detailed results:
const results2 = sweepLine.detailed(fc);