Documentation to extend VM tests (#25101)
Documentation to extend VM tests (#25101)

* first readme

* address maasen's comments

* lint

* lint

* address tao's comments

* update readme

* address Michael's comments

* lint

* addresssing comments

* update

* address Tao's comments
istio/istio,istio/istio,istio/istio,istio/istio,istio/istio