primary-menus: Clarify whether About menu item should mention application name
According to https://developer.gnome.org/hig/stable/primary-menus.html the primary (☰) menu should have an item named About.
According to https://gitlab.gnome.org/GNOME/Initiatives/wikis/App-Menu-Retirement the menu item should be named About Widget Factory where the app's name is Widget Factory.
I guess the HIG needs to be updated.
cc/ @aday