async function minifiedFiles(dir) {
  return await new Promise((res, rej) => {
    glob(dir + "/**/*.min.{js,css}", {}, (err, files) => {
      if (err) {
        rej(err);
      } else {
        res(files.map((f) => f.replace(dir + "/", "")));
      }
    });
  });
}
Returns list of minified files in the given directory.