:memo: Add a line to the docs

docs/api/notification.md

@@ -104,9 +104,12 @@ HTML5 Notification implementation, simply instantiating a `new Notification` doe
 not immediately show it to the user, you need to call this method before the OS
 will display it.
 
+If the notification has been shown before, this method will dismiss the previously
+shown notification and create a new one with identical properties.
+
 #### `notification.close()`
 
-Dismisses the notification
+Dismisses the notification.
 
 ### Playing Sounds