constructor({ name, data }) {
    this.name = name;
    this.data = data;
    Object.defineProperty(this, 'data', {
      enumerable: false,
      writable: true,
      value: data,
    });
    Object.defineProperty(this, 'chunkCrc', {
      enumerable: true,
      get() {
        return crc32(this.name, this.data);
      }
    });
    Object.defineProperty(this, 'chunkLength', {
      enumerable: true,
      get() {
        return this.data.byteLength;
      }
    });
  }
A generic PNG chunk with a chunk name and data.