Fix: Trigger avmap.io rebuild on staging branch merges

This ensures the staging cache updates trigger a rebuild of avmap.io staging site.
Previously, merging to staging would update the cache but not notify avmap.io.

Author: jacksonlester

.github/workflows/update-avmap.yml

@@ -2,7 +2,7 @@ name: Update avmap.io Data
 
 on:
   push:
-    branches: [main]
+    branches: [main, staging]
     paths:
       - 'events.csv'
       - 'geometries/**'