[mapbox-gl] add LngLat.distanceTo (#43084)

types/mapbox-gl/index.d.ts

@@ -1056,6 +1056,10 @@ declare namespace mapboxgl {
         /** Return a LngLat as a string */
         toString(): string;
 
+        /** Returns the approximate distance between a pair of coordinates in meters
+         * Uses the Haversine Formula (from R.W. Sinnott, "Virtues of the Haversine", Sky and Telescope, vol. 68, no. 2, 1984, p. 159) */
+        distanceTo(lngLat: LngLat): number;
+
         toBounds(radius: number): LngLatBounds;
 
         static convert(input: LngLatLike): mapboxgl.LngLat;

types/mapbox-gl/mapbox-gl-tests.ts

@@ -687,6 +687,7 @@ expectType<mapboxgl.LngLatLike>({ lon: 0, lat: 0 });
 
 new mapboxgl.LngLat(0, 0);
 expectType<mapboxgl.LngLat>(mapboxgl.LngLat.convert(lnglatlike));
+expectType<number>(new mapboxgl.LngLat(0, 0).distanceTo(new mapboxgl.LngLat(0, 0)));
 
 /*
  * LngLatBoundsLike