Update the kuberay-mcad.md

[tedhtchang]

Give clear instructions for any skill level user to follow. For example if applicable each step should be given a command

1. Install MCAD using instructions present under deployment directory should be followed by a command:

git clone https://github.com/project-codeflare/multi-cluster-app-dispatcher
cd multi-cluster-app-dispatcher
helm install mcad --set image.repository=quay.io/project-codeflare/mcad-controller --set image.tag=stable deployment/mcad-controller

2. Make sure MCAD has clusterrole to create ray resources, please patch using configuration file present in config directory with name xqueuejob-controller.yaml

kubectl apply -f doc/usage/examples/kuberay/config/xqueuejob-controller.yaml

[tedhtchang]

This should be updated along with the doc improvement issue.