Allow three elements in LngLat.convert, for GeoJSON

Following RFC 7946, position is an array of number with two OR MORE
elements (Implementations SHOULD NOT extend positions beyond three
elements). The 3rd element is usually Altitude. We could ignore it
but we must not fail.
This small fix allows well-formed geojson file to be fully processed

Signed-off-by: Olivier Guiter <oguiter@free.fr>

src/geo/lng_lat.js

@@ -107,7 +107,7 @@ class LngLat {
         if (input instanceof LngLat) {
             return input;
         }
-        if (Array.isArray(input) && input.length === 2) {
+        if (Array.isArray(input) && (input.length === 2 || input.length === 3)) {
             return new LngLat(Number(input[0]), Number(input[1]));
         }
         if (!Array.isArray(input) && typeof input === 'object' && input !== null) {

test/unit/geo/lng_lat.test.js

@@ -23,8 +23,13 @@ test('LngLat', (t) => {
 
     t.test('#convert', (t) => {
         t.ok(LngLat.convert([0, 10]) instanceof LngLat, 'convert creates a LngLat instance');
+        t.ok(LngLat.convert([0, 10, 0]) instanceof LngLat, 'convert creates a LngLat instance (Elevation)');
+        t.throw(() => {
+            LngLat.convert([0, 10, 0, 5]);
+        }, "LngLat must not accept an array size bigger than 3'", 'detects and throws on invalid input');
         t.ok(LngLat.convert({lng: 0, lat: 10}) instanceof LngLat, 'convert creates a LngLat instance');
         t.ok(LngLat.convert({lng: 0, lat: 0}) instanceof LngLat, 'convert creates a LngLat instance');
+        t.ok(LngLat.convert({lng: 0, lat: 0, elev: 0}) instanceof LngLat, 'convert creates a LngLat instance');
         t.ok(LngLat.convert(new LngLat(0, 0)) instanceof LngLat, 'convert creates a LngLat instance');
         t.throws(() => {
             LngLat.convert(0, 10);