add nginx demo for image updater

manifests/nginx-demo/deployment.yaml

@@ -0,0 +1,23 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-demo
+  annotations:
+    # 👇 These lines tell Argo CD Image Updater what to watch and how to update
+    argocd-image-updater.argoproj.io/image-list: nginx=nginx
+    argocd-image-updater.argoproj.io/nginx.update-strategy: latest
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: nginx-demo
+  template:
+    metadata:
+      labels:
+        app: nginx-demo
+    spec:
+      containers:
+      - name: nginx
+        image: nginx:1.27
+        ports:
+        - containerPort: 80

manifests/nginx-demo/service.yaml

@@ -0,0 +1,10 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: nginx-demo
+spec:
+  selector:
+    app: nginx-demo
+  ports:
+  - port: 80
+    targetPort: 80