How to create a signal for a webkitdirectory input

import { createSignal, type Component } from 'solid-js';

const App: Component = () => {
  const [files, setFiles] = createSignal(/* What do I put here? */)
  return (
    <main>
      <form onsubmit={(ev) => ev.preventDefault()}>
        {/* @ts-expect-error */}
        <input type="file" id='files' webkitdirectory directory multiple />
        <input type='submit' value="Submit" />
      </form>
    </main>
  );
};

export default App;