2023: Add registration information and #FlockIreland hashtag
    
    This commit adds more information about the conference registration and
    links out to the Eventbrite page set up for Flock. Attendees can receive
    or optionally purchase a ticket for the event. Tickets are required for
    entry to the venue for security and building code compliance purposes.
    
    It also adds a second hashtag to distinguish this year's Flock from any
    other before it: #FlockIreland. This way, we have the continued use of
    the #FlockToFedora hashtag across many years, and the new one for
    memories and moments specific to this year's event.
    
    Signed-off-by: Justin W. Flory (he/him) <jwf@redhat.com>