title: How to show TabBar label only on active Tab?
body: <p>I would like to hide the TabBar Label when the tab is not active.
  With <code>showLabel</code> from tabBarOptions I can only disable them completely.
  Thanks in advance.</p>
  
  <p><a href="https://i.stack.imgur.com/Pyke1.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Pyke1.png" alt="Material Design TabBar"></a></p>