moved PtrJNode map to YGJtypes.h and passing layout context as data in LayoutPassEnd Event

Summary: Move PtrJNodeMap to header file so that it can be accessed in events subscribers outside yoga

Reviewed By: davidaurelio

Differential Revision: D15619629

fbshipit-source-id: 1bf213efd38ec7bcac6a38070f21fa837c5f17da

yoga/event/event.h

@@ -71,5 +71,10 @@ struct Event::TypedData<Event::NodeDeallocation> {
   YGConfig* config;
 };
 
+template <>
+struct Event::TypedData<Event::LayoutPassEnd> {
+  void* layoutContext;
+};
+
 } // namespace yoga
 } // namespace facebook