Added quiet zone / border option

[nosrevi]

Added quiet zone / border option. I understand that you can use css margin as stated in issue #21, but when you save the QR code as an image, there's no border. This can cause the QR code not recognizable. I reproduced the issue when saving the image on the cellphone.

I set the default border size to 4 module according to ISO/IEC 18004 standard.

[kosso]

:+1: This is exactly what I needed. Thanks.

[alexanderdino]

Thanks for the commit! I wonder why this haven't been merged yet.

Also, did you notice that there is a thin grey border on the top of the QRCode?

[PierreTrp]

Works like a charm thanks

[crozone]

Ran into this issue when implementing Dark Mode on my website - the QR code will not scan if there isn't a white region surrounding it.

Given how many times this issue has been reported, are any of the maintainers around to review/merge this?