feat(integrations): add support for langchain and langsmith

[jjmachan]

No description provided.

[hinthornw]

@jjmachan happy to help if there's anything blocking this release! Would love to land so we can share more broadly (https://github.com/langchain-ai/langsmith-cookbook/blob/main/testing-examples/ragas/ragas.ipynb)

[jjmachan]

thanks for the catch @mspronesti 🙌🏽

ps: will add docs soon but feel free to look at https://notes.explodinggradients.com/en/latest/RAG-Experiments/basecamp-handbook/baseline-langchain.html for how to use this in action, I'll docs in the mean time

[mspronesti]

@jjmachan I accidentally misspelled Optional with an "r" in my suggestion. Beware 😅

[jjmachan]

no worries - I missed it but at least our linters caught it 😂