Add excursion option

Change-Id: I70133582d92c3a6385fefb46a99743d47f68cd46
diff --git a/config.php.example b/config.php.example
index 722ed0f..4f67a19 100755
--- a/config.php.example
+++ b/config.php.example
@@ -24,6 +24,7 @@
 $EARLYBIRD_CONFERENCE_FEE = 240;
 $CONFERENCE_DINNER = 60;
 $STUDENT_DISCOUNT = 80;
+$EXCURSION = 20;
 $EARLYBIRD_DEADLINE = "15 May 2023"; // HAWAIAN TIME (HST) is used :)
 
 // Redis password