title: TWTweetComposeViewController doesn't show link preview
body: <p>When I add a link to a tweet in the TWTweetComposeViewController, I see the link attached correctly:</p>
  
  <p><img src="https://i.stack.imgur.com/ypnLy.png" alt="enter image description here"></p>
  
  <p>But unlike when I do so in Safari, the link doesn't show a preview of the URL like Safari (or Youtube) does:</p>
  
  <p><img src="https://i.stack.imgur.com/hc7w1.png" alt="enter image description here"></p>
  
  <p>Do you know if it's a hidden feature or if it depends on the Link added to the tweet?</p>
  
  <p>Thank you!</p>