updated README

Author: snehmehta

README.md

@@ -25,8 +25,15 @@ import { openEnsembleApp } from 'ensemble-react-native';
 
 Install dependency: `yarn install`
 
+[optional]
+Change appId: 
+- Go to `ensemble_app/ensemble/ensemble-config.yaml`
+- change `appId`
+
 Build flutter files: `cd ensemble_app && flutter build aar --no-tree-shake-icons`
 
+Note: If their is any change in `ensemble_app` you need to re-run above build aar command
+
 Move to main repo: `cd ..`
 
 Run on android: `yarn example android`