Tray icon does not indicate if everything is up-to-date

Hi,

I saw in the doc that it says

Tray icon indicates when it is connected to syncthing (no status updates yet).

so this issue is to make sure it does not get forgotten :-)

It's good to see if syncthing is running locally or not, but what I also really want to see is if my files are all synced correctly or not.
If any folder or any remote device is not up-to-date, I think the colour of the icon should change to draw the user's attention.
Right now I regularly visit the web interface to make sure everything is green. I really wish the icon would give me that information.

Note: if there are events like a "receive only" folder becoming out of sync then I think the icon should also indicate there is something not 100% ok, so that the user knows he should visit the web interface to see what's going on, and eventually click the "revert local changes" button in that case.

Thanks!

No files, tests, or entry points are named. Start by locating the tray icon status handling and the existing Syncthing connection/status integration; define the icon states for fully synced, out of date, and receive-only or otherwise unhealthy folders, then verify that each state is visible without opening the web interface.