Dear Spectacle Team,
I really wish you could add a feature to scan QR codes to your great application.
Kind regards,
G. B.
Its a bit buried, but already implemented 
You need to install the prison package. Then you capture a region, accept it, and in the captured image window, there will be a message bar popup annocungin the found code (and its content).
Its a bit counterintuitive to discover and use, as the bar code/QR code reading has an entirely different ux approach than OCR. Here Im propposing a unified experience for content extraction.