Add pointer to pretix booking site

Author: willGraham01

index.md

@@ -18,7 +18,7 @@ helper: ["TBC", "TBC"]     # boxed, comma-separated list of helpers' names, like
 email: ["[email protected]", "[email protected]"]    # boxed, comma-separated list of contact email addresses for the host, lead instructor, or whoever else is handling questions, like ["[email protected]", "[email protected]", "[email protected]"]
 collaborative_notes:  # optional: URL for the workshop collaborative notes, e.g. an Etherpad or Google Docs document (e.g., https://pad.carpentries.org/2015-01-01-euphoria)
 eventbrite:           # optional: alphanumeric key for Eventbrite registration, e.g., "1234567890AB" (if Eventbrite is being used)
-pretix: # Optional: url bit that points to pretix event "organisation/eventid"
+pretix: "ARC/2024-11-27-hpcc/" # Optional: url bit that points to pretix event "organisation/eventid"
 ---
 
 {% comment %} See instructions in the comments below for how to edit specific sections of this workshop template. {% endcomment %}