Barby::QrCode does not implement valid? method

[Achimba]

Therefore any calls to validate Barby::QrCode will always return false since this is the default value of the base class Barby::Barcode.

Reproduction:
barcode = Barby::QrCode.new('1234567890')
barcode.valid? == false

All of the other Symbologies implement valid? method. I think that QrCode should too.