tray icon - sync folder behavior

[MeijeSibbel]

If double clicking on the tray icon, the sync folder opens, but then if people double click on it again, a new window opens (two windows now). From user feedback i found that they find this annoying as then they have to manually close all the open windows for each double click. I noticed this myself too.

We should just bring the window that is already opened to the foreground.

[jkawamoto]

Memo: Using this library https://github.com/thraaawn/winctl seems one possible solution.