On https://github.com/mozilla/pdf.js/wiki/Required-Browser-Features we mention required browser features for PDF.js, but I have the feeling that not all of them are necessary nowadays since we moved to using more modern features over the years. Moreover, as indicated in https://github.com/mozilla/pdf.js/issues/11950#issuecomment-637149085, some features may be missing such as range requests or `async/await`.

In short, we should verify which are still necessary and update the wiki page and the automated feature detection if possible.
if (checkCanvas('plus-loaded'))
          promise.resolve({ output: 'Failed', emulated: 'Yes' });
        else
          promise.resolve({ output: 'Failed', emulated: 'No' });
      }, 2000);
      return promise;
    },
    impact: 'Important',
    area: 'Core'
  },
  {
    id: 'Worker',
    name: 'Worker is present',
    run: function () {
      if (typeof Worker != 'undefined')
        return { output: 'Success', emulated: '' };
      else
        return { output: 'Failed', emulated: 'No' };
    },
    impact: 'Important',
    area: 'Core'
  },
  {
    id: 'Worker-Uint8Array',
    name: 'Worker can receive/send typed arrays',
    run: function () {
      if (typeof Worker == 'undefined')
        return { output: 'Skipped', emulated: '' };
     try {
        var worker = new Worker('worker-stub.js');