Don't add notifications twice + persiste them.

src/main.js

@@ -29,7 +29,7 @@ Vue.use(VueTimeago, {
 })
 
 const persistedStateOptions = {
-  paths: ['users.users']
+  paths: ['users.users', 'statuses.notifications']
 }
 
 const store = new Vuex.Store({

src/modules/statuses.js

@@ -173,8 +173,11 @@ const addNewStatuses = (state, { statuses, showImmediately = false, timeline, us
   }
 
   const addNotification = ({type, status, action}) => {
+    // Only add a new notification if we don't have one for the same action
+    if (!find(state.notifications, (oldNotification) => oldNotification.action.id === action.id)) {
       state.notifications.push({type, status, action, seen: false})
     }
+  }
 
   const favoriteStatus = (favorite) => {
     const status = find(allStatuses, { id: toInteger(favorite.in_reply_to_status_id) })