Add Brighton 2024 CFP (#570)

Author: andycroll

_data/conferences.yml

@@ -2543,6 +2543,8 @@
   url: https://brightonruby.com
   twitter: brightonruby
   mastodon: https://ruby.social/@brightonruby
+  cfp_phrase: CFP closes
+  cfp_date: 2024-02-29
 
 - name: Madison+ Ruby 2024
   location: Madison, WI