Add support for OllamaFunctions chat model from the official langchain library

Ollama current doesn't support [Open AI Compatible Function Calling](https://github.com/ollama/ollama/issues/2790) but there are models such as [Hermes 2 Pro](https://huggingface.co/NousResearch/Hermes-2-Pro-Mistral-7B) that supports function calling - https://ollama.com/adrienbrault/nous-hermes2pro.

LangChain Python has [OllamaFunctions](https://python.langchain.com/v0.1/docs/integrations/chat/ollama_functions/) ([src](https://github.com/langchain-ai/langchain/blob/master/libs/experimental/langchain_experimental/llms/ollama_functions.py)), LangChain Javascript has an equivalent [OllamaFunctions](https://js.langchain.com/docs/integrations/chat/ollama_functions#passing-in-functions) ([src](https://github.com/langchain-ai/langchainjs/blob/main/examples/src/models/chat/ollama_functions/custom_prompt.ts)). We should have something similar to unblock ollama users from using function call before ollama has an official support.