Shim: Non-blocking Polyfill [Promise, fetch, Object.assign, URLSearchParams]

shim.html

<script>
  window.Promise || document.write('<script src="https://unpkg.com/[email protected]/dist/es6-promise.min.js"><\/script>');
  window.fetch || document.write('<script src="https://unpkg.com/[email protected]/fetch.js"><\/script>');
  window.URLSearchParams || document.write('<script src="https://unpkg.com/@ungap/[email protected]/min.js"><\/script>');
  Object.assign=Object.assign||function(r){for(var n,a=1;a<arguments.length;a++)for(var s in n=arguments[a]||{})n.hasOwnProperty(s)&&(r[s]=n[s]);return r};
</script>