Fix: Add missing torch and psutil dependencies to CUDA installation instructions - #3162

📄 Description of Changes:

This PR updates the Install with Nvidia CUDA section in the README to prevent installation failures caused by missing dependencies.

Issue

Users attempting to install instructlab[cuda] may encounter the following errors:

• ModuleNotFoundError: No module named 'torch'
• ModuleNotFoundError: No module named 'psutil'

Fix

• Updated the installation steps to explicitly install torch and psutil before running pip install instructlab[cuda].
• Ensured that these dependencies are in place to prevent package resolution failures.

Changes Made

• Modified the Install with Nvidia CUDA section in README to include:

  pip install torch psutil

  before installing instructlab[cuda].

Issue resolved by this Pull Request:
Resolves # (Add issue number if applicable)

🛠️ How to Test

1. Set up a fresh virtual environment:

   python -m venv venv && source venv/bin/activate

2. Follow the updated installation steps from the README.
3. Verify that torch and psutil are installed correctly:

   python -c "import torch; print(torch.__version__)"

   Expected output: Torch version installed correctly.
4. Verify that instructlab[cuda] installs without issues.

✅ Checklist

• Commit Message Formatting: Commit titles and messages follow guidelines in the [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/#summary).
• Changelog Updated: (if applicable) Updated [CHANGELOG.md](https://github.com/instructlab/instructlab/blob/main/CHANGELOG.md) with notable changes.
• [x ] Documentation Updated: (if applicable) Updated documentation reflecting the changes.
• Unit Tests Added: (if applicable) Added unit tests for the changes.
• Functional Tests Added: (if applicable) Added functional tests to verify the changes.
• E2E Workflow Tests Added: (if applicable) Added E2E workflow tests.