Add fedora compose ostree repo to fedora-repos-ostree subpackage
    
    This will allow community members to more easily test development
    builds because the remote information for the compose ostree repo
    will already be on the system. That means they'll be a simple
    `rpm-ostree rebase fedora-compose:<ref>` away from testing out a
    development version.
    
    Signed-off-by: Dusty Mabe <dusty@dustymabe.com>