Minimal modern setImmediate polyfill

setImmediate.ts

// Draft uses YuzuJS/setImmediate polyfill, which can be reduced to this code.
// But it seems request requestAnimationFrame is good enough.
// TODO: Will it work with queue fix?
// // https://github.com/google/closure-library/blob/master/closure/goog/async/nexttick.js#L209
const setImmediate = (() => {
  const channel = new MessageChannel();
  let head: any = {};
  let tail = head;
  channel.port1.onmessage = () => {
    if (head.next !== undefined) {
      head = head.next;
      const { callback } = head;
      head.callback = null;
      callback();
    }
  };
  return (callback: () => void) => {
    tail.next = { callback };
    tail = tail.next;
    channel.port2.postMessage(0);
  };
})();