title: How to add button to bottom navigation bar which hang out above - Flutter
body: <p>I have bottom navigation bar with center item that looks like on this picture: </p>
  
  <p><a href="https://i.stack.imgur.com/BD50Xl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BD50Xl.png" alt=""></a></p>
  
  <p>How to implement such a thing in Flutter?</p>
  
  <p>I found that every icon that I put into BottomNavigatonBarItem is fitted inside navigation bar's bounds. But I need it to be hanged out above.</p>