Improve QR code character input function

[tokohito]

Thank you for sharing such a useful tool! I'm looking forward to Bluetooth support, but there is one more feature I would like. Please add the function to write line breaks, catalog format, or both in QR codes.

It would be nice to be able to insert newline characters in the CODE string, or read an external template file for this requirement.

catalog formats knowlage https://github.com/zxing/zxing/wiki/Barcode-Contents

external template file example https://github.com/leplusorg/docker-qrcode

best regards.