addMarker method
Add a marker on the map point
and returned callback
when you clicked on it
Implementation
@override
addMarker(LatLng point, Function(LatLng point)? callback) {
if (callback != null) {
super.markers[point] = callback;
}
js_util.globalContext.callMethodVarArgs('_addMarker'.toJS, [point.latitude.toJS, point.longitude.toJS]);
}