title: CSS: allow textarea to grow with contents up to a limit
body: <p>On certain sites (eg Github), the textareas have a set <code>min-height</code> and <code>max-height</code>.  As the user types into them, they grow with content until they reach their max height. Then vertical scroll bars appear.</p>
  
  <p>How is this effect accomplished?  My textarea does not grow with its contents even though it hasn't reached the specified <code>max-height</code></p>
  
  <pre><code>textarea{
    width:100%;
    min-height:80px;
    max-height:200px;
    overflow:auto;
  }
  </code></pre>
  
  <p><a href="https://codepen.io/anon/pen/qqMjaP" rel="nofollow noreferrer">Look at this demo</a></p>