title: The tag 'script' is disallowed except in specific forms
body: <p>I started my first amp html. But using the code from here:
  <a href="https://www.ampproject.org/docs/get_started/create/basic_markup" rel="nofollow noreferrer">https://www.ampproject.org/docs/get_started/create/basic_markup</a></p>
  
  <p>Shows me an error on Google Chrome for this tag:</p>
  
  <pre><code>&lt;script async src="https://cdn.ampproject.org/v0.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>Error Message:
  <strong>The tag 'script' is disallowed except in specific forms.</strong></p>