Create an informative issue (See each section, incomplete templates/issues won't be triaged)

Using the current documentation as a model, please complete the issue template. 

Note: Doc team updates the current version and the two previous versions (n-2). For earlier versions, we will address only high-priority, customer-reported issues for releases in support.

Prerequisite: Start with what we have

Always look at the current documentation to describe the change that is needed. Use the source or portal link for Step 4:

 - Use the Customer Portal: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes

 - Use the GitHub link to find the staged docs in the repository: https://github.com/stolostron/rhacm-docs 

Describe the changes in the doc and link to your dev story

Provide info for the following steps:

1. - [x] Mandatory Add the required version to the Fix version/s field.

2. - [ ] Mandatory Choose the type of documentation change.

      - [ ] New topic in an existing section or new section
      - [x] Update to an existing topic

3. - [x] Mandatory for GA content:
            
       - [x] Add steps and/or other important conceptual information here: 
       

Define the image content source policy yaml with your mirror registries and save it to the file `icsp.yaml`

cat << EOF >> icsp.yaml
- mirrors:
  - brew.registry.redhat.io
  source: registry.redhat.io
- mirrors:
  - brew.registry.redhat.io
  source: registry.stage.redhat.io
- mirrors:
  - brew.registry.redhat.io
  source: registry-proxy.engineering.redhat.com
EOF 

hcp create cluster agent \
    --name=${HOSTED_CLUSTER_NAME} \
    --pull-secret="${PULL_SECRET_FILE}" \
    --agent-namespace=${HOSTED_CONTROL_PLANE_NAMESPACE} \
    --base-domain=${BASEDOMAIN} \
    --api-server-address=api.${HOSTED_CLUSTER_NAME}.${BASEDOMAIN} \
    --ssh-key ${HOME}/.ssh/id_rsa.pub \
    --namespace ${CLUSTERS_NAMESPACE} \
    --release-image=quay.io/openshift-release-dev/ocp-release:${OCP_RELEASE} \
    --image-content-sources icsp.yaml 

Ensure the flag `--image-content-sources` is specified in the create cluster command

       
       - [x] Add Required access level for the user to complete the task here: (same as what's in the document already https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.9/html/clusters/cluster_mce_overview#creating-a-hosted-cluster-bm)

       - [ ] Add verification at the end of the task, how does the user verify success (a command to run or a result to see?)
     
     
       - [x] Add link to dev story here: (bug) https://issues.redhat.com/browse/HOSTEDCP-1427

4. - [x] Mandatory for bugs: What is the diff? Clearly define what the problem is, what the change is, and link to the current documentation: 

Problem: When a user uses a mirror registry, they need to specify an ICSP yaml file and provider that as the --image-content-sources the hcp create cluster command.

Change: (see above) add instruction for defining the image content source policy file with their mirror registry and then providing that file in the create cluster command 

Document: The create cluster command is here: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.9/html/clusters/cluster_mce_overview#creating-a-hosted-cluster-bm     

Unsure: Is there another doc or section for hypershift and disconnected/mirror registries, it might fit better there. If not, then please create a separate section in this document