docs: Add enable Cloud Messaging note

README.md

@@ -38,9 +38,11 @@ export default defineNuxtConfig({
 
 - `firebaseConfig` Firebase project configuration
 - `vapidKey` Public server key provided to push services [docs](https://firebase.google.com/docs/cloud-messaging/js/client?authuser=0#configure_web_credentials_with)
-- `serviceAccount` Firebase admin credentials [docs](https://firebase.google.com/docs/admin/setup?authuser=0#initialize_the_sdk_in_non-google_environments). You can ignore this property in case the app server is not needed.
+- `serviceAccount` Firebase admin credentials [docs](https://firebase.google.com/docs/admin/setup?authuser=0#initialize_the_sdk_in_non-google_environments). You can ignore this property in case the app server is not needed
 
-4. Add firebase messaging service worker by creating `firebase-messaging-sw.js` file under `public` folder
+4. If you are using app server, make sure to enable `Cloud messaging API` [docs](https://firebase.google.com/docs/cloud-messaging/server#firebase-admin-sdk-for-fcm)
+
+5. Add firebase messaging service worker by creating `firebase-messaging-sw.js` file under `public` folder
 
 ```js
 // public/firebase-messaging-sw.js