TurfMisc#nearestPointOnLine does not report distance along the route

Capturing from https://turfjs.org/docs/#nearestPointOnLine, the Feature returned from TurfMisc#nearestPointOnLine should return a location number property that describes the distance along the route of the computed intersection point, next to already available dist number property which describes the distance to the original point. Also would be great to explain those properties in the Javadoc and add public constant instead of relying on raw strings for dist and location.

/cc @cafesilencio

Inizia da TurfMisc#nearestPointOnLine e confronta il Feature restituito con la documentazione di nearestPointOnLine su turfjs.org/docs/. Il lavoro è completato quando il risultato include una proprietà di posizione della distanza del percorso e le proprietà dist/location sono spiegate in Javadoc, sostituendo le stringhe grezze con costanti pubbliche.