title: React Navigation: styling TabNavigator text
body: <p>I am using <a href="https://reactnavigation.org/" rel="noreferrer">React Navigation</a> in a create-react-native-app.</p>
  
  <p>I am using the <code>TabNavigator</code> component like this (iPhone SE):</p>
  
  <p><a href="https://i.stack.imgur.com/VntwT.png" rel="noreferrer"><img src="https://i.stack.imgur.com/VntwT.png" alt="enter image description here"></a></p>
  
  <p>The <code>TabNavigator</code> is the dark blue strip with 'Job #1', 'Chat', Files', 'Details.</p>
  
  <p>I want to customise the text of these items. I want non-uppercase text (which as far as I know is impossible to achieve with React Native Stylesheet), and to apply a fix for the 'Details' item which is wrapping onto two lines.</p>
  
  <p>I have looked through the React Navigation API at TabNavigator but have not been able to find the answer.</p>
  
  <p>How can I style these items?</p>