feat: Add support for HuggingFace hosted models

[cvauclair]

Model Provider Integration Request

HuggingFace hosts many open source models (including many fine-tuned models) and provides an API to interact with them.

Resources

Unlike many of the existing providers, the HuggingFace API has many task-specific endpoints (for instance, a text classification endpoint).

However, since Rig does not support task-specific endpoints, the integration would most likely use one of the following generic text completion endpoints:

• chat completion
• text completion

Note: The HuggingFace API does not endpoints for generating embeddings. The integration would therefore be limited to chat completion only.