[hybridkubernetes] - Lack of guidance for installing azure-arc agents

### Link
https://github.com/Azure/azure-rest-api-specs/blob/main/specification/hybridkubernetes/resource-manager/Microsoft.Kubernetes/stable/2021-10-01/connectedClusters.json

### Problem Description
[az connectedk8s](https://learn.microsoft.com/en-us/azure/azure-arc/kubernetes/quickstart-connect-cluster?tabs=azure-cli#connect-an-existing-kubernetes-cluster) makes a k8s arc-enabled by [creating a connected cluster resource](https://github.com/Azure/azure-cli-extensions/blob/47e48bf7b1a8d2bd1fe47b3bfb989f272b60429f/src/connectedk8s/azext_connectedk8s/custom.py#L366) and [installing azure-arc agents](https://github.com/Azure/azure-cli-extensions/blob/47e48bf7b1a8d2bd1fe47b3bfb989f272b60429f/src/connectedk8s/azext_connectedk8s/custom.py#L373).
However, if users want to enable azure-arc by other ways(like REST API), they can use the [PUT API](https://learn.microsoft.com/en-us/rest/api/hybridkubernetes/connected-cluster/create?tabs=HTTP) to create a connected cluster, but it seems [this overview](https://learn.microsoft.com/en-us/azure/azure-arc/kubernetes/conceptual-agent-overview#deploy-agents-to-your-cluster) does not provide detailed scripts which can directly or intuitively guide users to install an agent. Is it possible to add the more friendly scripts for users to install the agent?

Start with the linked connectedClusters.json API specification, the referenced azext_connectedk8s/custom.py sections, and the Azure Arc agent overview. Determine where installation guidance belongs and document an intuitive script-based path for users who create a connected cluster through the REST API. Done means the overview provides actionable agent-installation instructions beyond the Azure CLI flow.

Written by the indexing model from the issue text.