I just created new grav plugin. It adds new feature to Grav - web push notifications: https://github.com/devlom/grav-plugin-webpush
You probably saw that notifications all over the web. Service is handled by OneSignal (just like similar plugin for Wordpress).
Right now plugin awaits it’s addition to Grav GPM, hopefully it will be accepted so you can install it with ease. At least right now you can install it manually from link above.
Let me know what you think.