System tray documentation

[Michael Giuffrida]

I've added a page to the site about the Ash system tray. It's basically a list of the system tray items and when they're visible. Hopefully this will be useful for QA/testing, for example with my WIP CL to add the status area to OOBE.

If you notice anything wrong or want to add to this list, please update the doc!

Thanks,

Michael