Support Hugging Face models (#215)

* support hf direct models

llms/hf_llm/README.md

@@ -0,0 +1,75 @@
+## Generate Text with MLX and :hugs: Hugging Face
+
+This an example large language model text generation that can pull models from
+the Hugging Face Hub.
+
+### Setup
+
+Install the dependencies:
+
+```
+pip install -r requirements.txt
+```
+
+### Run
+
+```
+python generate.py --model <model_path> --prompt "hello"
+```
+
+For example:
+
+```
+python generate.py --model mistralai/Mistral-7B-v0.1 --prompt "hello"
+```
+
+will download the Mistral 7B model and generate text using the given prompt.
+
+The `<model_path>` should be either a path to a local directory or a Hugging
+Face repo with weights stored in `safetensors` format. If you use a repo from
+the Hugging Face Hub, then the model will be downloaded and cached the first
+time you run it. See the [Models](#models) section for a full list of supported models.
+
+Run `python generate.py --help` to see all the options.
+
+
+### Models
+
+The example supports Hugging Face format Mistral and Llama-style models.  If the
+model you want to run is not supported, file an
+[issue](https://github.com/ml-explore/mlx-examples/issues/new) or better yet,
+submit a pull request.
+
+Here are a few examples of Hugging Face models which work with this example:
+
+- [mistralai/Mistral-7B-v0.1](https://huggingface.co/mistralai/Mistral-7B-v0.1)
+- [meta-llama/Llama-2-7b-hf](https://huggingface.co/meta-llama/Llama-2-7b-hf)
+- [TinyLlama/TinyLlama-1.1B-intermediate-step-1431k-3T](https://huggingface.co/TinyLlama/TinyLlama-1.1B-intermediate-step-1431k-3T)
+
+Most
+[Mistral](https://huggingface.co/models?library=transformers,safetensors&other=mistral&sort=trending)
+and
+[Llama](https://huggingface.co/models?library=transformers,safetensors&other=llama&sort=trending)
+style models should work out of the box.
+
+### Convert new models 
+
+You can convert (change the data type or quantize) models using the
+`convert.py` script. This script takes a Hugging Face repo as input and outputs
+a model directory (which you can optionally also upload to Hugging Face).
+
+For example, to make 4-bit quantized a model, run:
+
+```
+python convert.py --hf-model <hf_repo> -q
+```
+
+For more options run:
+
+```
+python convert.py --help
+```
+
+You can upload new models to the [Hugging Face MLX
+Community](https://huggingface.co/mlx-community) by specifying `--upload-name``
+to `convert.py`.