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.
console.log("  " + taskName);
  });
  done();
});
gulp.task("buildnumber", function (done) {
  console.log();
  console.log("### Getting extension build number");
  exec(
    "git log --format=oneline " + config.baseVersion + "..",
    function (err, stdout, stderr) {
      var buildNumber = 0;
      if (!err) {
        
        buildNumber = stdout ? stdout.match(/\n/g).length : 0;
      } else {
        console.log(
          "This is not a Git repository; using default build number."
        );
      }
      console.log("Extension build number: " + buildNumber);
      var version = config.versionPrefix + buildNumber;
      exec('git log --format="%h" -n 1', function (err2, stdout2, stderr2) {
        var buildCommit = "";
        if (!err2) {
          buildCommit = stdout2.replace("\n", "");
        }
        createStringSource(
          "version.json",
          JSON.stringify(
            {