store secrets for cert manager in the current repo

kubernetes/rpi5-cluster/apps/cert-manager/cert-manager.yaml

@@ -1,5 +1,23 @@
 apiVersion: kustomize.toolkit.fluxcd.io/v1
 kind: Kustomization
+metadata:
+  name: secrets
+  namespace: flux-system
+spec:
+  interval: 1h
+  path: ./kubernetes/rpi5-cluster/apps/cert-manager/
+  prune: true
+  sourceRef:
+    kind: GitRepository
+    namespace: flux-system
+    name: home-cluster-ops
+  decryption:
+    provider: sops
+    secretRef:
+      name: sops-age
+---
+apiVersion: kustomize.toolkit.fluxcd.io/v1
+kind: Kustomization
 metadata:
   name: cert-manager
   namespace: cert-manager