Add wordpress example for demonstrating variable reference

examples/wordpress/patch.yaml

@@ -0,0 +1,23 @@
+apiVersion: apps/v1beta2
+kind: Deployment
+metadata:
+  name: wordpress
+spec:
+  template:
+    spec:
+      initContainers:
+      - name: init-command
+        image: debian
+        command:
+        - "echo $(WORDPRESS_SERVICE)"
+        - "echo $(MYSQL_SERVICE)"
+      containers:
+      - name: wordpress
+        env:
+        - name: WORDPRESS_DB_HOST
+          value: mysql
+        - name: WORDPRESS_DB_PASSWORD
+          valueFrom:
+            secretKeyRef:
+              name: mysql-pass
+              key: password