title: AMP: amp-accordion not working
body: <p>Can anybody provide a working example of an <code>amp-accordion</code>? When I try the example code from <a href="https://www.ampproject.org/docs/reference/extended/amp-accordion.html" rel="nofollow noreferrer">https://www.ampproject.org/docs/reference/extended/amp-accordion.html</a> in an amp page that references </p>
  
  <pre><code>&lt;script async custom-element="amp-accordion" src="https://cdn.ampproject.org/v0/amp-accordion-0.1.js"&gt;&lt;/script&gt; 
  </code></pre>
  
  <p>in the header, I get the following two (disturbing) error messages: </p>
  
  <pre><code>The attribute 'custom-element' in tag 'amp-access extension .js script' is set to the invalid value 'amp-accordion'. (see https://www.ampproject.org/docs/reference/extended/amp-access.html)
  </code></pre>
  
  <p>and finally</p>
  
  <pre><code>The tag 'amp-accordion' is disallowed.
  </code></pre>
  
  <p>Any ideas?</p>