Add class registration comment hint for main branch

src/register_types.cpp

@@ -11,6 +11,7 @@ void initialize_gdextension_types(ModuleInitializationLevel p_level)
 	if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) {
 		return;
 	}
+	//ClassDB::register_class<YourClass>();
 }
 
 void uninitialize_gdextension_types(ModuleInitializationLevel p_level) {