Add URL option for push notification

[ghost]

I need to send a URL from my NVR to my phone via a push notification so that when I tap the notification, it takes me to the NVR’s recording that generated the alert.

Something like this

message: 'test message'
data:
android:
notification:
url: https://www.google.com

Thanks!

[allanpersson]

Duplicate of #162 🙏 extended notifications is work in progress 😇