title: Altering the font size (and, if possible, other font formatting attributes) of the Shell class' back button's overridden text
body: <p>I have a <code>ContentPage</code> (that is a content of the sub-classed <code>Shell</code> class) which, when viewed requires a back button with a specific string text to be present in the navigation bar.</p>
  <pre><code>&lt;ContentPage 
      ....&gt;
    &lt;Shell.NavBarIsVisible&gt;True&lt;/Shell.NavBarIsVisible&gt;
      &lt;Shell.BackgroundColor&gt;Black&lt;/Shell.BackgroundColor&gt;
      &lt;Shell.BackButtonBehavior&gt;
          &lt;BackButtonBehavior IsEnabled=&quot;True&quot; 
                              TextOverride=&quot;A&quot; /&gt;
      &lt;/Shell.BackButtonBehavior&gt;
    
     .....
  
  &lt;/ContentPage&gt;
  </code></pre>
  <p>The back button with the required text is displayed as expected in the navigation bar, but the text is not quite in the required font size in the Android platform.</p>
  <p>As always with such problems, I attempted to resolve the issue by using a custom shell renderer for the Android platform (as seen below), but I am not able to fathom the way to alter the font size of the text of the back button.</p>
  <pre><code>class ShellRenderer
              : ShellRenderer
  {
      public ShellRenderer
              (Context context) : base(context) { }
  
      protected override IShellToolbarAppearanceTracker 
          CreateToolbarAppearanceTracker()
      {
          return new CustomToolbar(this);
      }
      
      public class CustomToolbar 
                    : ShellToolbarAppearanceTracker
      {
          public CustomToolbar
                 (IShellContext context) : base(context) 
          { 
          }
  
          public override void SetAppearance
            (AndroidX.AppCompat.Widget.Toolbar toolbar,
             IShellToolbarTracker toolbarTracker, 
             ShellAppearance appearance)
          {
              base.SetAppearance
                  (toolbar, toolbarTracker, appearance);
  
              // How do you increase the font size of the back button??
              
          }
      }
  }
  </code></pre>
  <p>Thanks in advance.</p>