code: function copyFile (src, dest) {
    return new Promise((resolve, reject) => {
      const read = fs.createReadStream(src);
      read.on('error', reject);
      const write = fs.createWriteStream(dest);
      write.on('error', reject);
      write.on('finish', resolve);
      read.pipe(write);
    })
  }
docs: copy file to dir
  @param src
  @param dest
  @returns {Promise<any>}