NK_WINDOW_SCROLL_AUTO_HIDE doesn't work for groups?

Just ran into this. Confirmed it by adding the flag to a group in the overview demo. The window scrollbar disappears but the group scrollbar does not. I don't see how I could be doing anything wrong.

The original commit is [here](https://github.com/Immediate-Mode-UI/Nuklear/commit/ebfeeea7e1d4b428c9e6b8c501599b1b81588a35) just for reference. While it doesn't explicitly mention groups in the commit message, I don't see any documentation or comment anywhere that says it's not supported and the documentation comments do say "Groups are basically windows inside windows".

I took a cursory glance at it in the debugger when it wasn't working and while the relevant code is hit it seems like group data isn't stored the same way as window data because my watch point was just overwritten by garbage randomly. Eventually I'll take the time to really understand how Nuklear handles its data but if anyone knows what's going on chime in please.

In the meantime, while it would be very nice if groups were supported, for now we should at least document clearly which window flags are not supported for groups in the larger comment blocks.

Start with the overview demo and the original commit linked in the issue, then trace handling for NK_WINDOW_SCROLL_AUTO_HIDE when applied to groups. Check the relevant larger comment blocks for documented group limitations. Done means either group scrollbars support the flag or the unsupported window flags are clearly documented.

Written by the indexing model from the issue text.