add comment to notification.ts

frontend/src/hooks/notification.ts

@@ -3,5 +3,7 @@ import { useContext } from 'react'
 
 export const useNotify = () => {
   const { notify, setMessage } = useContext(NotificationContext)
+  // setMessage can be used to change a notification's message without creating a new one
+  // use this to create a progress bar etc.
   return { notify, setMessage }
 }