Add Desktop notifications (#252)

Add Desktop notifications (#252)

* Add notifications

* Abide push actions

* Handle browsers not having notification support

* Ask for notification permission after loading

* Make usePermission work without live permission support

* Focus message when clicking the notification

* make const all caps

* Fix usePermission error in Safari

* Fix live permissions

* Remove userActivity and use document.visibilityState instead

* Change setting label to "desktop notifications"

* Check for notification permissions in the settings.js