docs: Add an example YAML file for the usage of the 'network' field.

[googs1025]

What would you like to be added:
I noticed that there are no relevant examples for the 'network' field in examples/simple. I would like to add an example in examples/simple, for instance, on how to use the 'Subdomain' and 'PublishNotReadyAddresses' fields. Additionally, I would like to document how to access pods through a headless service.
Why is this needed:
Let users know how to access each other's pods in the jobset through headless svc

[googs1025]

/assign

[googs1025]

@kannon92 @danielvegamyhre @ahg-g Do we need it?

[kannon92]

Sounds good to me! Thank you for the suggestion.

[ahg-g]

Most existing examples already use that, but I am ok if you want to add something under https://github.com/kubernetes-sigs/jobset/tree/main/examples/simple