[DOC] - Add docs for node_groups.launch_template

[viniciusdc]

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

With the recent work done on nebari-dev/nebari#2668, it's now possible to include custom pre-bootstrap commands during EC2 instance initialization and custom AMIs for your deployment. This issue should track documentation of these parameters and an example as well as any warnings that should be forwarded to the users. and

Steps to Resolve this Issue

1. Update node_groups config section to describe the new parameters
   ...