title: react-native resize <ScrollView/> when keyboard is open
body: <p>I have a react-native simple chat app, which looks like this</p>
  
  <pre><code>+-----------------
  |     Header     |
  +----------------+
  |                |
  |                |
  |    Messages    |
  |                |
  |                |
  +----------------+
  |   Write here   |
  +----------------+
  </code></pre>
  
  <p>What I want to achieve is that when I open the keyboard the Messages View to shrink (decrease height)  and I can be able to see the header and the text input as well, as I see now when I open keyboard the App is keeping the sizes but the keyboard is pushing all the content to top.</p>