Annotation boundaries should also be affected by opacity

Currently opacity will change the inside of an annotation, but the borders of the annotation remain at 100%. It would be helpful if these were either paired, or there was a separate option for reducing/changing the opacity of the borders, as this sometimes makes it hard to judge where some ascenders, notes, of staff lines stop or start when near other glyphs. @JoyfulGen would be curious for your feel on this as well!