title: Get Download URL from Firebase Storage in Flutter
body: <p>I'm currently exploring Flutter, I found there is an official Firebase Storage plugin in Flutter <a href="https://pub.dartlang.org/packages/firebase_storage" rel="noreferrer">firebase_storage</a>
  I have storage reference like this one:</p>
  
  <pre><code>final StorageReference ref = FirebaseStorage.instance.ref().child("default.png");
  </code></pre>
  
  <p>But there is no method to get download URL from that StorageReference. </p>