feat: AI / ML API Usage example

[D1m7asis]

✅ PR Title: examples: AI / ML API Usage example

📝 Description

Added a minimal example demonstrating how to use AI/ML API as a model provider with quivr-core. Includes both basic and streaming usage via ChatOpenAI.

• 📁 Files added: simple_question.py, simple_question_streaming.py
• 📄 Added minimal pyproject.toml and README.md for clarity and reproducibility
• 📦 Includes quivr-core as a local/remote dependency (depending on use)

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✅ Checklist

• Follows Quivr style and example structure
• Self-reviewed and tested locally
• Added usage docs and comments
• Tests not applicable (example script)

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📸 Screenshots / Logs

Not applicable — CLI example

[D1m7asis]

⚠️ Heads up: The ReadTheDocs build is failing due to a global build config issue, not this PR.

This PR only adds usage examples in examples/, with no changes to docs/ or build scripts.

If needed, I can help debug .readthedocs.yaml, but for now this seems unrelated to the changes introduced here.

[D1m7asis]

@StanGirard hi! Can i get a review here pls? Thanks!