A way to modify alpha of several shapes at once (similar to CanvasGroup for UI)

Hi!

UI in Unity has a really neat component (CanvasGroup) that allows to modify alpha of several child UI objects. This is very useful for complex UI layouts, as it also allows nesting.

With shapes, I need to combine several shapes into complex groups, and it would be super useful to have a way to modify their alpha for the whole group.

Thanks!