title: How can I get an element by xpath?
body: <p>I need to find any element in DOM by xpath. I already tried the following:</p>
  
  <pre><code>let el = await page.$x('//*[@id="readium-right-panel"]/ul/li[1]');
  </code></pre>
  
  <p>The returning error is:</p>
  
  <blockquote>
    <p>TypeError: page.$x is not a function</p>
  </blockquote>