title: Xamarin Custom control not showing in toolbox
body: <p>Even though I have marked my custom Xamarin forms control with the following. It is still not showing in the Xamarin forms toolbox any reason as to why that may note I am using a .netstandard shared Libary to house my controls inside a NuGet if that makes any difference.</p>
  
  <p>It is a progress bar and I want the end-user to be able to drag it into the xaml. In the same way the entry textbox works.</p>
  
  <pre><code>[XamlCompilation(XamlCompilationOptions.Compile)]
  [DesignTimeVisible(true)]
  [Category("Appearance")]
  </code></pre>