title: Chrome extension: how to avoid refresh extension when develop content.js
body: <p>I'm on developing a chrome extension, most logic code is in the <code>content.js</code>, what upset me is, when the <code>content.js</code> code updated, I have to </p>
  
  <ol>
  <li>Refresh extension by myself</li>
  <li>Refresh the test web page</li>
  </ol>
  
  <p>Is there something like <code>supervisor</code> in <code>node.js</code>, </p>
  
  <p>when the <code>content.js</code> updated, it automatic refresh the extension even the web page?</p>