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.
);
}
gulp.task(
  "mozcentral-pre",
  gulp.series("buildnumber", "default_preferences", function () {
    console.log();
    console.log("### Building mozilla-central extension");
    var defines = builder.merge(DEFINES, { MOZCENTRAL: true });
    var MOZCENTRAL_DIR = BUILD_DIR + "mozcentral/",
      MOZCENTRAL_EXTENSION_DIR = MOZCENTRAL_DIR + "browser/extensions/pdfjs/",
      MOZCENTRAL_CONTENT_DIR = MOZCENTRAL_EXTENSION_DIR + "content/",
      FIREFOX_EXTENSION_DIR = "extensions/firefox/",
      MOZCENTRAL_L10N_DIR = MOZCENTRAL_DIR + "browser/locales/en-US/pdfviewer/",
      FIREFOX_CONTENT_DIR = EXTENSION_SRC_DIR + "/firefox/content/";
    
    rimraf.sync(MOZCENTRAL_DIR);
    var versionJSON = getVersionJSON();
    var version = versionJSON.version,
      commit = versionJSON.commit;
    
    const MOZCENTRAL_COMMON_WEB_FILES = [
      ...COMMON_WEB_FILES,
      "!web/images/*.cur",
    ];
    return merge([
      createMainBundle(defines).pipe(
        gulp.dest(MOZCENTRAL_CONTENT_DIR + "build")
      ),
      createScriptingBundle(defines).pipe(
        gulp.dest(MOZCENTRAL_CONTENT_DIR + "build")