:page_facing_up: LICENSE: Add Fedora default content license
    
    This commit adds the Creative Commons Attribution-ShareAlike 4.0
    International license to the repository as the default license for all
    content stored here. Technically, this is implied already because of
    Fedora's existing legal policies and documentation, but this makes an
    implicit assumption into an explicit definition. It also ensures the
    license is copied between git repo clones and forks.
    
    The legal text was pulled directly from Creative Commons:
    
    https://creativecommons.org/licenses/by-sa/4.0/legalcode.txt
    
    Signed-off-by: Justin W. Flory (he/him) <jwf@redhat.com>