Group count: option to show it reduce as items are selected?

[moloko]

If you have react-select set up with 'grouped' options, it's a little odd that the 'group count' remains the same when options from that group have been selected.

It's particularly noticeable if isMulti is enabled - when you can end up with something like this where it show the 'Flavours' count as 4 despite there being only one flavour remaining in that group:

Appreciate that this might well be the desired behaviour - but as things stand I don't think there's any (easy) way to do this by using something like formatGroupLabel since the only data made available to it is OptionsType - which doesn't allow for any way of finding out how many options in that group remain unselected.