add ap-southeast-5 (#517)

Author: duncanista

ci/datasources/regions.yaml

@@ -11,6 +11,7 @@ regions:
   - code: "ap-southeast-2"
   - code: "ap-southeast-3"
   - code: "ap-southeast-4"
+  - code: "ap-southeast-5"
   - code: "ap-northeast-1"
   - code: "ap-northeast-2"
   - code: "ap-northeast-3"