Add slack alters for HelmRelease success

kubernetes/rpi5-cluster/flux-system/notification-controller/slack-alerts.yaml

@@ -9,4 +9,18 @@ spec:
   channel: general
   address: https://slack.com/api/chat.postMessage
   secretRef:
-    name: slack-bot-token
+    name: slack-bot-token
+---
+apiVersion: notification.toolkit.fluxcd.io/v1beta3
+kind: Alert
+metadata:
+  name: release-success-notification
+spec:
+  eventSources:
+    - kind: HelmRelease
+      name: '*'
+  inclusionList:
+    - ".*succeeded.*"
+  eventMetadata:
+    app.kubernetes.io/env: "home-rpi5-cluster"
+    app.kubernetes.io/cluster: "rpi5-cluster"