code: async function readBytes ({ file, start, chunkSize }) {
    const buffer = Buffer.alloc(chunkSize)
  
    const fileDescriptor = await fs.open(file, 'r')
  
    const { bytesRead } = await fs.read(
      fileDescriptor,
      buffer,          // buffer to write to
      0,               // offset in the buffer to start writing at
      chunkSize,       // number of bytes to read
      start            // where to begin reading from in the file
    )
  
    // Slice the buffer in case chunkSize > fileSize - start
    return buffer.slice(0, bytesRead)
  }
docs: Read `chunkSize` bytes from the given `file`, starting from byte number `start`.
  
  @param {string} file      - path to a file
  @param {number} start     - byte to start reading from
  @param {number} chunkSize - number of bytes to read
  @returns {Promise<Buffer>}