src: make ObjectWrap dtor virtual

Otherwise, subclasses of `ObjectWrap` would not be deleted
correctly by the `delete instance;` line in `FinalizeCallback()`.

(This is also just the right thing to do for classes from which
subclasses are supposed to be created.)

napi-inl.h

@@ -3865,7 +3865,7 @@ inline napi_value ObjectWrap<T>::InstanceSetterCallbackWrapper(
 
 template <typename T>
 inline void ObjectWrap<T>::FinalizeCallback(napi_env env, void* data, void* /*hint*/) {
-  T* instance = reinterpret_cast<T*>(data);
+  ObjectWrap<T>* instance = static_cast<ObjectWrap<T>*>(data);
   instance->Finalize(Napi::Env(env));
   delete instance;
 }