Adding RLHF

[hkzak2]

with the current hype on RLHF I think it would really nice if we can implement that on top of the text retrieval models so that we can further improve the the responses from the Q&A retrieval models.

[JasperLS]

That's a great idea, and I can imagine many users might be interested in it. Would you ming opening a Proposal documenting your use-case. Here is the process for creating a new proposal: https://github.com/deepset-ai/haystack/tree/main/proposals?