doc: show kustomization

README.md

@@ -58,3 +58,29 @@ The webhook is deployed using standard Kubernetes manifests:
 - Service
 - MutatingWebhookConfiguration
 - ImagePullSecret (to be injected into pods)
+
+## Production Configuration
+
+For production use, you should create a configmap with your specific configuration. Create a kustomization.yaml file like this:
+
+```yaml
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+namespace: imagepullsecrets-system
+resources:
+  - imagepullsecret.yaml
+configMapGenerator:
+  - name: imagepullsecrets-webhook-config
+    envs:
+      - imagepullsecret.env
+    options:
+      disableNameSuffixHash: true
+```
+
+And create an `imagepullsecret.env` file with your environment variables:
+
+```env
+REGISTRY_MAPPINGS=harbor.yourdomain.com:regcred-harbor
+IGNORED_REGISTRIES=k8s.gcr.io,gcr.io,quay.io,docker.io
+SOURCE_NAMESPACE=imagepullsecrets-system
+```