Notification + Sound on successful sync

### Describe the feature you'd like to request

Having Notification visual and sound options (in my case Desktop browser plugin scope) would be helpful to notify the user that a sync has happened (upload/download/whatever). Pretty simple, common settings to turn notifications on/off plus sound on/off or other customisation stuff. Maybe even two default sounds, one for sync upload, one for sync download. And the settings local per-device (or maybe global server-side is a good idea? dunno).

### Describe the solution you'd like

Already wrote this above.

### Describe alternatives you've considered

I'm not aware of any alternatives for this request.