An example of a web push notification on a desktop device.
Set API_KEY, SENDER_ID at index.html.
Request to FCM using curl
curl
-d '{"data": {"title": "Message title", "body": "Message body"} "to": "Instance ID"}'
-H "Content-Type: application/json"
-H "Authorization: key=App key"
-X POST "https://fcm.googleapis.com/fcm/send"