[Request] groupMultiselect scroll support #526

Is your feature request related to a problem? Please describe.
When groupMultiselect is passed too many items they escape outside the current viewport and cannot be seen.

groupSelect might also have this problem, but I haven't checked.

Scrolling up is not a solution either as moving the cursor will reset the scroll to the bottom again.

Funnily enough, autocompleteMultiselect supports scrolling in a way that would be perfect for groupMultiselect!

Describe the solution you'd like

Scrolling behavior similar to autocompleteMultiselect

Additional context

Currently blocking merging the @clack/prompts migration in Changesets:
changesets/changesets#1879