Add additional best-effort region for AMI publishing (#159)

Author: grahamc

.github/workflows/publish.yml

@@ -148,7 +148,8 @@ jobs:
             --run-id "${{ github.run_id }}-${{ github.run_attempt }}" \
             --copy-to-regions \
             --public \
-            --best-effort-region me-central-1
+            --best-effort-region me-central-1 \
+            --best-effort-region me-south-1
 
   prune-old-amis:
     name: Prune old AMIs