How to use:

Create val
import wrapper from "https://esm.town/v/substrate/substrateBadgeMiddleware";

async function handler(req: Request): Promise<Response> {
  const html = `
    <h1>Hello, world</h1>
  `;
  return new Response(html, {
    headers: {
      "Content-Type": "text/html; charset=utf-8",
    },
  });
}

export default wrapper(handler, import.meta.url);

reference: https://www.val.town/v/jxnblk/valTownBadge