title: Custom scheme URL in macCatalyst app doesn't work
body: <p>I have a macCatalyst app, and I want to launch/open it from another app (e.g. Safari) via custom-scheme-URL along with parameters, something like <code>myCustomScheme://command?paramA=valueA</code>. As this is quite an usual pattern in iOS app, I can't get it work in macCatalyst.</p>
  <p>I keep receiving:</p>
  <pre><code>typeForContentsOfURL:error: must be overridden for your application to support non-'file:' URLs.
  </code></pre>
  <p>I have tried to eliminate above error by:</p>
  <ul>
  <li>override <code>-[NSDocumentController typeForContentsOfURL:error:]</code> in plug-in bundle, return some UTI string;</li>
  <li>specify custom extensions in <code>Info.plist</code> using <code>CFBundleTypeExtensions</code>;</li>
  </ul>
  <p>Neither <code>-application(_:open:options:)</code> of <code>AppDelegate</code> nor <code>-scene(_:openURLContexts:)</code> of <code>SceneDelegate</code> get called, although I could print out the custom URL in overriden method implemented in plug-in bundle.</p>
  <p>Note:</p>
  <ul>
  <li>custom scheme is already registered in <code>Target</code> -&gt; <code>Info</code> -&gt; <code>URL Types</code>;</li>
  </ul>
  <p>Did I miss something? Did I do something wrong? Can anyone help?</p>