Notification sounds (#367)

* Basic notification sound support

* Add settings option for notification sounds

* Allow sound without desktop notifications

src/client/state/cons.js

@@ -67,6 +67,7 @@ const cons = {
       TOGGLE_MEMBERSHIP_EVENT: 'TOGGLE_MEMBERSHIP_EVENT',
       TOGGLE_NICKAVATAR_EVENT: 'TOGGLE_NICKAVATAR_EVENT',
       TOGGLE_NOTIFICATIONS: 'TOGGLE_NOTIFICATIONS',
+      TOGGLE_NOTIFICATION_SOUNDS: 'TOGGLE_NOTIFICATION_SOUNDS',
     },
   },
   events: {
@@ -135,6 +136,7 @@ const cons = {
       MEMBERSHIP_EVENTS_TOGGLED: 'MEMBERSHIP_EVENTS_TOGGLED',
       NICKAVATAR_EVENTS_TOGGLED: 'NICKAVATAR_EVENTS_TOGGLED',
       NOTIFICATIONS_TOGGLED: 'NOTIFICATIONS_TOGGLED',
+      NOTIFICATION_SOUNDS_TOGGLED: 'NOTIFICATION_SOUNDS_TOGGLED',
     },
   },
 };