Update GLTFLoader.js

[JSDoc] Specify that loadMesh return type can include `THREE.Group`

examples/js/loaders/GLTFLoader.js

@@ -1943,7 +1943,7 @@ THREE.GLTFLoader = ( function () {
 	/**
 	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
 	 * @param {number} meshIndex
-	 * @return {Promise<THREE.Mesh|THREE.SkinnedMesh>}
+	 * @return {Promise<THREE.Group|THREE.Mesh|THREE.SkinnedMesh>}
 	 */
 	GLTFParser.prototype.loadMesh = function ( meshIndex ) {