Add example showing the use of Mapbox vector tiles

externs/example.js

@@ -9,3 +9,10 @@ var common;
  * @return {string} Renderer type.
  */
 common.getRendererFromQueryString = function() {};
+
+
+/**
+ * @return {function((ol.Feature|ol.render.Feature), number):
+ *     Array.<ol.style.Style>}
+ */
+var createMapboxStreetsV6Style = function() {};