Update README to clarify addon invocation behavior in CLI

Author: urumo

readme.md

@@ -251,4 +251,4 @@ func MyAddon(cluster *types.Cluster, logger *utils.Logger)
 
 - Use the provided helpers in `pkg/clusterutils` for manifest application, Helm, and readiness checks.
 - Addons should be idempotent and log all actions.
-- Addons are invoked automatically if their corresponding CLI flag is set.
+- Addons are invoked automatically if their corresponding CLI flag is set.