Add RubyJax - Open Hax December 2025

Author: marcoroth

_data/meetups.yml

@@ -8633,3 +8633,10 @@
   start_time: 19:00:00 +08
   end_time: 20:00:00 +08
   url: https://www.meetup.com/ruby-malaysia/events/fnnnstyhcqbhc
+
+- name: RubyJax - Open Hax December 2025
+  location: Jacksonville, FL
+  date: 2025-12-30
+  start_time: 18:30:00 EDT
+  end_time: 20:00:00 EDT
+  url: https://www.meetup.com/rubyjax/events/llklbtyhcqbnc