fix(generateImages): Fix rehearsal marks not having a box around them due to node canvas restriction.
fix(generateImages): Fix rehearsal marks not having a box around them due to node canvas restriction.

also, shift rehearsal mark slightly more downwards again to old y position (see Bolivia sample)

seems like the .height attribute only exists with SVG (and browser canvas probably)

opensheetmusicdisplay/opensheetmusicdisplay,opensheetmusicdisplay/opensheetmusicdisplay,opensheetmusicdisplay/opensheetmusicdisplay