[OBSOLETE] Adding a QR code

This snippet lets you draw a QR-code, for example to provide a link to the composer's, or the music editor's website.

Actually encoding the URL into a QR-code is not done here (this just draws the QR-code from a grid of "black" or "white" values), but see the code for a short Python snippet you can use to avoid having to fill for each small square if it's black or white.

This snippet is obsolete starting from LilyPond 2.25.3, which adds a \qr-code markup command that takes a URL directly instead of a grid of "black" and "white" values. It is used like \markup \qr-code #10 "https://lilypond.org".