title: Add onTap listener to appBar (Flutter)
body: <p>We need to add onTap listener to appBar. Not an <code>actions</code> or <code>leading</code> button. We need it for all appBar. 
  I tried to use <code>InkWell</code>, but it has visual effect, we no need it.
  I tried to use <code>GestureDetector</code>, but it works only when user tapping on the text in this <code>GestureDetector</code>.</p>