treewide: clarify the maintainer situation on packages lacking one
    
    The status quo is that any Parabola hacker is expected to (be able to)
    modify any packages, and having a single maintainer of a package
    discourages that practice as people would typically send a patch to
    the maintainer instead of pushing it directly.
    
    So for a start we can add common maintainership on package lacking any
    "Maintainer: " header for packages in repositories that are supposed
    to be maintained.
    
    Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>