Update document to adding argocd CLI to create applications

[gyliu513]

What steps did you take and what happened:

We need to update document to adding argocd CLI to create applications, so that the CICD or some test tools can leverage argocd CLI to do gitops.

What did you expect to happen:

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:

• Minikube/KIND version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):
• Instana version:
• Crossplane version: