libre: your-sanity: Add PKGBUILD license
    
    Freemor agreed to use the CC0 licenses for all the ebuilds made by
    pers[1].
    
    [1] On the 27 April 2021 on #parabola on liberachat we have:
        02:31 < Freemor> re: PKGBUILD license - I'm fine with both the CC)
        and the README
    
    Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>