ChatWrapper Implementation for Llama3

[cereniyim]

Checked

• I searched existing ideas and did not find a similar one
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• I've clearly described the feature request and motivation for it

Feature request

We have a chat application and we recently updated the underlying model to Llama3. However, we had to hardcode the prompt formatting of Llama3 because Chatwrapper implementation doesn't support this model yet.

Motivation

We can implement a custom ChatModel but Llama3 is getting more popular everyday. So, it can be more efficient and clean to implement this within langchain_experimental.chat_models.llm_wrapper

Proposal (If applicable)

I propose adding a ChatWrapper implementation for Llama3. Thank you!