title: Easiest way to add 3 dot pop up menu AppBar in Flutter
body: <ol>
  <li><p>I want a 3 dot popup menu button in the app bar of my app </p></li>
  <li><p>It must be a clickable one [navigate to other widgets,pages]</p></li>
  <li><p>Please tell how to add a pop up menu button in  a simpler way </p></li>
  </ol>