Feature summary (what you would like to be able to do and where):
Currently, the QR code is downloaded with the filename qrcode.svg. It would be good to make it possible to customize this.
Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
When downloading multiple QR codes from different wiki pages it becomes necessary to manually rename each as you download them. Although the Special:QrCode supports codes for all URLs a common use case is for simple wiki page URLs, and in that case the page name could be used for the QR code.
Benefits (why should this be implemented?):
Avoids users having to set manual filenames, or ending up with files named qrcode (1).svg, qrcode (2).svg, etc.