flocktofedora.org: Add platinum and silver sponsors
    
    Add logos for Rocky Linux and AlmaLinux as sponsors for Flock 2023 in
    Cork, Ireland. I also changed formatting for the sponsor lines to make
    them easier to edit for me should I have more logos to add soon.
    
    Signed-off-by: Justin W. Flory (he/him) <jwf@redhat.com>