Allow grace notes to be attached to rests

Your idea

In MuseScore, grace notes that are to be played before the beat are entered using the somewhat confusingly named "grace note after" element, which puts them at the end of the previous beat.

This element can only be attached to notes. We should allow it to be attached to rests as well as notes.

Problem to be solved

It is not possible to enter a sequence such as this where the grace notes occur after a rest and before a barline.

Final measures of Liza Lehmann's - 2 Seal Songs, No. 2 - "You mustn't swim till you're six weeks old". IMSLP #626778

Prior art

I guess an alternative solution would be to allow the normal grace note ("grace note before") to be attached to barlines.

However, that wouldn't work when the grace note occurs in the middle of a bar, and you want it to play before the beat. In that situation you would need to use the "grace note after" element, which may involve attaching it to a rest.

Additional context

Workaround: Attach the "grace note after" to an invisible non-playing note in a higher voice.