Add documentation for using Radius with Argo CD

[rynowak]

What content needs to be created or modified?

We're missing documentation for using Radius with Argo CD. This is one of the more popular CD technologies for Kubernetes, so the question will come up a lot.

Describe the solution you'd like

Describe how users can use Argo CD with Radius through the Kubernetes API: like in https://docs.radapp.io/tutorials/helm/

Users that are using Radius with tools like Helm, Kustomize, or any other Kubernetes-manifest-based technology can start using Argo CD today.

We'll need to do some product work to enable Argo for Bicep-based deployments. See: radius-project/radius#6942

Where should the new material be placed?

This should be it's own page. We will need a section (eventually) for CD technologies, where Argo CD belongs.

AB#10736