title: Adding a shell flyout item header
body: <p>In Xamarin Shell I'm trying to add a header to a flyout item. See the picture below (taken from the Xaminals project).</p>
  
  <p>The 'Categories' text is a header which is not clickable or navigatable, just a static template.</p>
  
  <p>I have found an article <a href="https://medium.com/@thebaileybrew/xamarin-forms-shell-lets-customize-the-flyout-menu-de3df2450f56" rel="nofollow noreferrer">here</a> but it's without source code and I haven't been able to construct a working example.</p>
  
  <p>How can I achieve something like this?</p>
  
  <p><a href="https://i.stack.imgur.com/4a1CQ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4a1CQ.png" alt="enter image description here"></a></p>