code: async function copyFile(srcPath, distPath) {
    await recursiveMkdir(path.dirname(distPath))
  
    return new Promise((resolve, reject) => {
      fs.createReadStream(srcPath).pipe(fs.createWriteStream(distPath))
        .on('finish', () => resolve())
        .on('error', err => reject(err))
    })
  }
docs: 拷贝文件