title: showDialog from root widget
body: <p>I want to show a dialog from root widget (the one that created MaterialApp) I have a <code>NavigatorState</code> instance, but showDialog requires context that would return <code>Navigator.of(context)</code>. </p>
  
  <p>It looks like I need to provide context from a route, but I can't do this, because the root widget does not have it.</p>
  
  <p>EDIT: I have found a workaround: I can push fake route that is only there to showDialog and then pop that route when dialog finishes. Not pretty but works.</p>