update instructions for unsloth training

[tymat]

The README is missing a python package which causes the following issue when running test_unsloth.py

root@f6861e54e0b3:/workspace/dgx-spark-playbooks/nvidia/unsloth/assets# python test_unsloth.py
/usr/local/lib/python3.12/dist-packages/torch/cuda/__init__.py:63: FutureWarning: The pynvml package is deprecated. Please install nvidia-ml-py instead. If you
did not install pynvml directly, please report this to the maintainers of the package that installed pynvml for you.
  import pynvml  # type: ignore[import]
🦥 Unsloth: Will patch your computer to enable 2x faster free finetuning.
🦥 Unsloth Zoo will now patch everything to make training faster!
Traceback (most recent call last):
  File "/workspace/dgx-spark-playbooks/nvidia/unsloth/assets/test_unsloth.py", line 48, in <module>
    model, tokenizer = FastModel.from_pretrained(
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/dist-packages/unsloth/models/loader.py", line 731, in from_pretrained
    model_types = get_transformers_model_type(
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/dist-packages/unsloth_zoo/hf_utils.py", line 112, in get_transformers_model_type
    raise RuntimeError(
RuntimeError: Unsloth: No config file found - are you sure the `model_name` is correct?
If you're using a model on your local device, confirm if the folder location exists.
If you're using a HuggingFace online model, check if it exists.

This is resolved by installing hf_transfer package.

[robert-mcdermott]

This was already fixed in this PR (yet to be merged): #14

[margaretz-nv]

@tymat thank you for raising the issue! I'll take it to the team to investigate.