[DOC] - Consider adding docs on how to add a new node group

Preliminary Checks

• This issue is not a question, feature request, RFC, or anything other than a bug report. Please post those things in GitHub Discussions: https://github.com/nebari-dev/nebari/discussions

Summary

It can be sometimes useful to add a new node group e.g. to isolate running argo workflows from the other nodes or when adding a gpu instance. This would be an advanced use case, not a default Nebari use case. We should consider adding docs on how to add a new node group.

I think for Azure, DO, and GCP this just consists of adding a nodeSelector (e.g. "cloud.google.com/gke-nodepool": node-group-name, "azure-node-pool": node-group-name, "doks.digitalocean.com/node-pool": node-group-name), but for aws I think you may need "eks.amazonaws.com/nodegroup" and the "dedicated": node-group-name node selector or it won't begin autoscaling without first manually scaling the node. See https://github.com/nebari-dev/nebari/pull/2168 for reference.

Steps to Resolve this Issue

See above

No target documentation file or test is named. Start by reviewing the existing Nebari documentation structure and pull request #2168, then verify the nodeSelector and autoscaling guidance for AWS, Azure, DigitalOcean, and GCP. Done means the advanced node-group setup is documented with provider-specific details and limitations.