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.
var timeout = setTimeout(function () {
          promise.resolve({ output: 'Failed', emulated: '?' });
        }, 5000);
        worker.addEventListener('message', function (e) {
          var data = e.data;
          if (data.action == 'xhr' && data.result)
            promise.resolve({ output: 'Success', emulated: '' });
          else
            promise.resolve({ output: 'Failed', emulated: 'Yes' });
        }, false);
        worker.postMessage({action: 'xhr'});
        return promise;
      } catch (e) {
        return { output: 'Failed', emulated: 'Yes' };
      }
    },
    impact: 'Important',
    area: 'Core'
  },
  {
    id: 'Canvas Blend Mode',
    name: 'Canvas supports extended blend modes',
    run: function () {
      var fail = { output: 'Failed', emulated: 'No' };
      var ctx = document.createElement('canvas').getContext('2d');
      ctx.canvas.width = 1;
      ctx.canvas.height = 1;
      var mode = 'difference';
      ctx.globalCompositeOperation = mode;
      if (ctx.globalCompositeOperation !== mode) {