[DOC] - Document pack setup as an admin

[kcpevey]

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

We need to create documentation for admin users, starting with how to set this pack up.

This should answer questions like:

• What are the yaml config options and what does each one do?
• How do I integrate nebi to this?
• How do I integrate MLflow to this?
• General JHub setup stuff like configuring different server sizes, etc (can be taken from nebari classic docs).

Some documentation exists in the README currently.

[andrewfulton9]

Noting that most of the above questions are already addressed in #92. MLflow is the only thing above not addressed.