FretDiagram : make the vertical offset a user adjustable parameter
In playing with the fretboard diagrams, I've wanted to move them closer to the staff. When we implement #24349: Set the size of fretboard offset text as part of the style, it would be nice to also provide a preference for this distance.
The target is in
setPos(-_spatium, -h -_spatium);
In my local copy, I've set it to:
Making this a preference would be ideal.