[DOC] - Add specific Login Step to Creating new environments page

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

Since the current default behavior is to not be logged into conda-store from Nebari, I suggest adding a specific login step to this page: https://www.nebari.dev/docs/tutorials/creating-new-environments

I would add it after the Preliminary reading section and before the Open conda-store web interface section.

I would then remove the sentance "If not logged in to conda-store, click on the "Log in" button in th left sidebar and authenticate similar to the Nebari login. This is required to be able to access many conda-store features."

Open the Creating new environments documentation page and review the sections around Preliminary reading and Open conda-store web interface. Add the requested login step between them and remove the duplicated login instruction; the page should clearly explain when authentication is required.