title: In Vite2, How to import an ESModule in tailwind.config.js
body: <p>Building a Vite2 app.</p>
  <p>tried to import an <code>ESModule</code> in <code>tailwind.config.js</code>.
  The Module was exported like:</p>
  <pre><code>export default xxx;
  </code></pre>
  <p>Then I imported the module in <code>tailwind.config.js</code> like:</p>
  <pre><code>const xx = require('./xx/xxx');
  </code></pre>
  <p>But I got an Error:</p>
  <pre><code>[plugin:vite:css] Cannot use import statement outside a module
  </code></pre>
  <p>How do I fix this?</p>