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

src/app/organisms/settings/Settings.scss

@@ -26,6 +26,12 @@
   }
 }
 
+.set-notifications {
+  &__not-supported {
+    padding: 0 var(--sp-ultra-tight);
+  }
+}
+
 .set-about {
   &__branding {
     margin-top: var(--sp-extra-tight);