title: How to set headerMode on some routes but not others. (React Navigation)
body: <p>With <a href="https://reactnavigation.org/" rel="noreferrer">React Navigation</a> Is it possible to define certain routes with a headerMode and others without?</p>
  
  <p>The majority of my pages don't use the header and I found how to turn it off globally.</p>
  
  <pre class="lang-js prettyprint-override"><code>export const App = StackNavigator({
    PhotoView: {
      screen: Photos
    },
    ListView: {
      screen: List
    }
  }, {
    headerMode: 'none'
  });
  </code></pre>
  
  <p>But if I wanted to show the header on <code>ListView</code> for example, how would I do that?</p>
  
  <p>I've tried several approaches from the docs but no luck.</p>