title: createPortal - TypeScript document.getElementById type issue when JavaScript runs fine?
body: <p>I'm trying to use ReactDOM.createPortal and neither 'ReactDOM' or 'document' is highlighted in VSCode and I get this error when hovering over 'document.getElementById('overlay-root')':</p>
  <pre><code>Argument of type 'HTMLElement | null' is not assignable to parameter of type 'Element'.
    Type 'null' is not assignable to type 'Element'.
  </code></pre>
  <p>Here's the code:</p>
  <pre><code>import styles from './CartModal.module.css';
  import ReactDOM from 'react-dom';
  import Card from '../UI/Card/Card';
  
  interface CartModalProps {
    onClose?: () =&gt; void
  }
  
  const DisplayCartModal: React.FC&lt;CartModalProps&gt; = (props) =&gt; {
  
    return ReactDOM.createPortal(
      &lt;&gt;
        &lt;CartModal /&gt;
      &lt;/&gt;, 
      document.getElementById('overlay-root')
    )
  }
  
  export default DisplayCartModal;
  </code></pre>
  <p>I've tried switching the file extension to .js to see if this is a TypeScript error and indeed when I changed it (and removed TS-specific syntax) everything was highlighted and worked perfectly. It did not return null, it returned the correct HTML Element. Help is <em>greatly</em> appreciated!</p>