add port-forward examples for sevice
```
$ kubectl port-forward --help
........
Examples:
# Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in the pod
kubectl port-forward pod/mypod 5000 6000
# Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in a pod selected by the
deployment
kubectl port-forward deployment/mydeployment 5000 6000
# Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in a pod selected by the
service
kubectl port-forward service/myservice 5000 6000
# Listen on port 8888 locally, forwarding to 5000 in the pod
kubectl port-forward pod/mypod 8888:5000
# Listen on a random port locally, forwarding to 5000 in the pod
kubectl port-forward pod/mypod :5000
........
```
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**What this PR does / why we need it**:
add port-forward examples for sevice
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #
**Special notes for your reviewer**:
**Release note**:
<!-- Write your release note:
1. Enter your extended release note in the below block. If the PR requires additional action from users switching to the new release, include the string "action required".
2. If no release note is required, just write "NONE".
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```release-note
add port-forward examples for sevice
```
Nikhita Raghunath