test.stubs
This option provides a more convenient way to overlay dummy packages. It also adds a function `config.lib.test.mkStubPackage` that can, e.g., be used for `package` options.
Also sets the default syncthing tray package to https://github.com/Martchus/syncthingtray instead of https://github.com/sieren/QSyncthingTray, which indirectly fixes #603