font-worker.js

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
  const response = await fetch(
    request.url.replace("https://fonts.jirafe.io", "https://fonts.googleapis.com"),
    request
  );

  const css = await response.text();

  return new Response(css.replace(/}/g, "font-display: swap; }"), {
    headers: response.headers
  });
}