[Docs] List Hugging Face Inference Provider

[hanouticelina]

This PR adds Hugging Face inference providers docs to https://ai.pydantic.dev/models/

cc @Kludex

[hyperlint-ai]

PR Change Summary

Added documentation for Hugging Face inference providers to the PydanticAI models site.

• Included Hugging Face as a new inference provider in the documentation
• Updated the index of model providers to reflect the addition of Hugging Face

Modified Files

• docs/models/index.md

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