Generate and save QR Code Image.
 
Basic Usage
    final generator = QRGenerator();
    await generator.generate(
      data: 'Hello World!',
      filePath: '$outputDir/hello.png',
    );
Full Usage
  Future saveQRImage() async {
    final generator = QRGenerator();
    await generator.generate(
      data: 'Hello World!',
      filePath: '$outputDir/hello.png',
      scale: 10,
      foregroundColor: Colors.yellow,
      backgroundColor: Colors.blue,
      errorCorrectionLevel: ErrorCorrectionLevel.medium,
      qrVersion: 4,
    );
  }
The Image will get saved to the provided filePath.
TODO