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 source = stream.Readable({ objectMode: true });
  source._read = function () {
    console.log();
    console.log("### Running " + testsName + " tests");
    var PDF_TEST = process.env.PDF_TEST || "test_manifest.json";
    var args = ["test.js"];
    switch (testsName) {
      case "browser":
        args.push("--reftest", "--manifestFile=" + PDF_TEST);
        break;
      case "browser (no reftest)":
        args.push("--manifestFile=" + PDF_TEST);
        break;
      case "unit":
        args.push("--unitTest");
        break;
      case "font":
        args.push("--fontTest");
        break;
      case "integration":
        args.push("--integration");
        break;
      default:
        this.emit("error", new Error("Unknown name: " + testsName));
        return null;
    }
    if (bot) {
      args.push("--strictVerify");
    }
    if (process.argv.includes("--noChrome")) {