Adding annotation example (#14440)

* Adding annotation example 

Adding example to show how annotation looks like in manifest.  This will help users to understand where exactly we can use the annotations whose details are already given on this page. Annotation `imageregistry: https://hub.docker.com/`  used intentionally to make it more relevant as earlier section talk about registry address  annotation.

* Resolving review comments

Resolving review comments

content/en/docs/concepts/overview/working-with-objects/annotations.md

@@ -69,6 +69,25 @@ If the prefix is omitted, the annotation Key is presumed to be private to the us
 
 The `kubernetes.io/` and `k8s.io/` prefixes are reserved for Kubernetes core components.
 
+For example, here’s the configuration file for a Pod that has the annotation `imageregistry: https://hub.docker.com/` :
+
+```yaml
+
+apiVersion: v1
+kind: Pod
+metadata:
+  name: annotations-demo
+  annotations:
+    imageregistry: "https://hub.docker.com/"
+spec:
+  containers:
+  - name: nginx
+    image: nginx:1.7.9
+    ports:
+    - containerPort: 80
+
+```
+
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