How to connect css to html in Google Apps Scripts
<p>I'm trying to make my first Google App. I have my HTML doc which has the include statement as outlined on <a href="https://developers.google.com/apps-script/guides/html/best-practices" rel="nofollow noreferrer">HTML Service: Best Practices</a>.</p>

<pre><code>&lt;html&gt;
    &lt;head&gt;
        &lt;base target="_top"&gt;
        &lt;?!= include('stylesheet') ?&gt;
    &lt;/head&gt;
    &lt;body&gt;
       ...
    &lt;/body&gt;
</code></pre>

<p>My code.gs file is as follows: </p>

<pre><code>function doGet() {
   return HtmlService.createTemplateFromFile('BooksTS2.html')
  .evaluate();
}
</code></pre>

<p>My style sheet is named stylesheet.html, and for testing purposes is really simple: </p>

<pre><code>&lt;style&gt;
   p {color: green;}
&lt;/style&gt;
</code></pre>

<p>But when I run it I get this error message: ReferenceError: "include" is not defined.</p>