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.
makefileContent += ".PHONY: " + targetsNames.join(" ") + "\n";
  return createStringSource("Makefile", makefileContent).pipe(gulp.dest("."));
});
gulp.task("importl10n", function (done) {
  var locales = require("./external/importL10n/locales.js");
  console.log();
  console.log("### Importing translations from mozilla-central");
  if (!fs.existsSync(L10N_DIR)) {
    fs.mkdirSync(L10N_DIR);
  }
  locales.downloadL10n(L10N_DIR, done);
});
gulp.task("gh-pages-prepare", function () {
  console.log();
  console.log("### Creating web site");
  rimraf.sync(GH_PAGES_DIR);
  
  return merge([
    vfs
      .src(GENERIC_DIR + "**/*", { base: GENERIC_DIR, stripBOM: false })
      .pipe(gulp.dest(GH_PAGES_DIR)),
    vfs
      .src(GENERIC_LEGACY_DIR + "**/*", {
        base: GENERIC_LEGACY_DIR,
        stripBOM: false,
      })
      .pipe(gulp.dest(GH_PAGES_DIR + "legacy/")),
    gulp
      .src("test/features/**/*", { base: "test/" })
      .pipe(gulp.dest(GH_PAGES_DIR)),