[O] Styling header stats for collapsed trees

[Daniele Nicolodi]

Hello,

there is a feature of Orgzly that I like: when a headline containing
sub-haedlines is folded, the leading star (bullet in Orgzly interface)
changes to signal that subheadings are hidden below.

I've tried to see if org allows to easily achieve something similar, but
the face of the headline and of the stars do not change when the
headline is collapsed.

Does anyone have a hint about something to hook upon to implement
something like that?

Thank you.

Cheers,
Dan