Expose Template Parameter for getFormattedChat

[a-ghorbani]

By exposing this parameter, we can enable users to customize and pass their templates, not just the ones that come with gguf.

[jhen0409]

This is easy to expose and it will be added soon, but I'll recommend user to use jinja parser for make prompt from template, currently the chat template in llama.cpp is a bit limited:

https://github.com/ggerganov/llama.cpp/blob/f245cc28d4eb900efad0bc740145f58d713c6e4f/src/llama.cpp#L21637-L21639