title: iOS push notification custom sound not able to figure out
body: <p>I have a <code>UNMutableNotificationContent</code> object in my AppDelegate class set up like so:</p>
  
  <pre><code>let content = UNMutableNotificationContent()
      content.title = "TITLE"
      content.body = "Friendly message"
      content.sound = UNNotificationSound.default()
  </code></pre>
  
  <p>In my Xcode build, I have a custom sound file called Wake-up-sounds.wav, and I am trying to set content.sound equal to this sound file, but I do not know how. How do I do this?</p>