[DOC] - Add docs on using local VS Code to remote tunnel into Nebari Jupyterlab

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 have docs on how to SSH into Nebari - https://www.nebari.dev/docs/how-tos/connect-via-ssh#connect-to-nebari-via-ssh . These work for the terminal in jlab, but they dont work for making a remote SSH connection to VSCode.

The instructions for connecting (via remote tunnel) a local VSCode instance to the remote JLab server are:

1. Download the vscode CLI for Linux x64 and upload to Nebari. The Code CLI is built into the desktop version, but you can just download the lighter CLI only. https://code.visualstudio.com/Download . For those who are particularly trusting, here is the shortcut: curl -LO https://code.visualstudio.com/sha/download?build=stable&os=cli-alpine-x64 .
2. Unpack it tar -xf vscode_cli.tar.gz
3. Add it to your system PATH in your ~/.bash_profile, e.g. export PATH="/path/to/codefolder:$PATH"
4. Source the updated ~/.bash_profile or get a new terminal
5. Follow the instructions here -https://code.visualstudio.com/docs/remote/tunnels#_using-the-code-cli

• In the Nebari terminal, run code tunnel
• Select github account for authentication and follow the instructions: To grant access to the server, please log into https://github.com/login/device and use code XXXX-XXXX.
• Give your Nebari machine a name
• It will output a URL to give you browser access from your local machine https://vscode.dev/tunnel/
• On your local machine, open VSCode and install the Remote - Tunnels extension from Microsoft
• On your local VSCode, click the "Accounts" button on the bottom left of VSCode.
• Select "Turn on Remote Tunnel Access" and follow the prompts, authenticating to Github again.
• Then Connect to Remote Tunnel and select

Theoretically most of this is discoverable by following https://code.visualstudio.com/docs/remote/tunnels#_using-the-code-cli but users don't know that SSH doesn't work with VSCode on Nebari but Remote tunneling does and this write up is much easier to follow (at least for me).

Start with the existing Nebari SSH documentation and the linked VS Code Remote Tunnels guide. Document the Linux x64 CLI download, extraction, PATH setup, code tunnel authentication, and local VS Code connection steps. Done means a user can follow the new instructions to connect a local VS Code instance to a remote Nebari JupyterLab server.