Add F31 release party organizer badge (closes #700)
    
    This commit adds the badge assets and a rule file for the F31 release
    party organizer badge. Even though it is a manually-awarded badge, I'm
    adding a rule file because it is more convenient (and faster) for the
    badge to be automatically created this way than me going into the Badges
    admin site and hand-typing the details there.
    
    Closes #700.
    
    Signed-off-by: Justin W. Flory <git@jwf.io>