[H] Document how to mirror chart repository for disconnected clusters

Document the following items for Helm Charts to work in disconnected environments:

• How to mirror images referenced by charts in a chart repository to a registry accessible by disconnected clusters, so that users can continue using Helm Charts on clusters that have restricted networks due to the organization's requirements.
• Helm charts in a disconnected environment need to have the option to host internal to the cluster (as default) or to an external repository that is still accessible to the cluster.
  • how to host the mirrored Helm chart repository in a cluster or somewhere else but accessible to the cluster
  • how to mirror images referred in images, or we can assume that images are already in the RedHat registry and there is already a known way how to mirror the Red Hat registry?
  • If there are some scripts that perform mirroring, or UX should be based on our UI and these scripts are shared, document them somewhere or just embed them into the documentation so that users can copy/paste them.

Note: There is existing documentation related to this that can be useful:

• Using the Cluster Samples Operator with an alternate registry
• Mirroring images for a disconnected installation

Additional information: https://docs.google.com/document/d/1POvXj_F61CMzKqCRrqZW4VEXHGVYIBuEup-WymM1xqQ/edit#heading=h.jayxfzskrf9e