Explicitly sets the AA_DontShowIconsInMenus attribute to false as it
defaults to true on some Qt versions / environments which causes icons
to not show up in the menus (e.g. MacOS).
see https://forum.qt.io/post/813228
The attribute has to be set on self.app after the QApplication has been
instanciated (https://doc.qt.io/qt-6/qt.html#ApplicationAttribute-enum)