title: React Native <Modal /> onDismiss not invoked
body: <p>Based on the code below, I would expect to see 'onDismiss!' when I swipe down on the modal view.</p>
  
  <p>When I swipe down on the modal view it does not invoke the provided function. I can't find any other React Native users experiencing this problem. I am using React Native version 0.60.6.</p>
  
  <p>Am I using Modal the wrong way or is this a bug?</p>
  
  <pre><code>&lt;Modal
    animationType="slide"
    presentationStyle="pageSheet"
    visible={showSetup}
    hardwareAccelerated
    onDismiss={() =&gt; alert('onDismiss!')}
    onRequestClose={() =&gt; alert('onRequestClose!')}
  &gt;
    &lt;SetupView closeView={() =&gt; this.willClose()} /&gt;
  &lt;/Modal&gt;
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/utU76.gif" rel="noreferrer"><img src="https://i.stack.imgur.com/utU76.gif" alt="enter image description here"></a></p>