I'm working on a Next.js project using the pages router, and the official documentation shows that this can be done by creating a page at pages/404.tsx:

export default function Custom404() {
  return <h1>404 - Page Not Found</h1>
}

How can I access the HTTP request headers here? Normally I would do it with the getServerSideProps, but the documentation says 404.js Cannot Have getInitialProps/getServerSideProps.

I just want to get the "accept-language" header so I the display text can be localized.