Include feature(Sub)Index in coordEach/Reduce (@turf/meta)

[DenisCarriere]

Include feature(Sub)Index in coordEach/Reduce

Implements Issue: #867

featureSubIndex can be a bit abstract when dealing with complex Geometries such as MutliPolygon, but for a simple LineString it is pretty useful knowing the exact coordinate position.

const features = turf.featureCollection([
    turf.lineString([[0, 0], [1, 1]]), // index 0
    turf.multiPoint([[4, 4], [0, 0]]), // index 1
    turf.point([3, 3]),                // index 2
    turf.lineString([[2, 2], [1, 1]])  // index 3
]);

turf.coordEach(features, (coord, coordIndex, featureIndex, featureSubIndex) => {
    // coordIndex      => 0, 1, 2, 3, 4, 5, 6
    // featureIndex    => 0, 0, 1, 1, 2, 3, 3
    // featureSubIndex => 0, 1, 0, 1, 0, 0, 1
})