Add support for json mode for OpenAI LLMs

[deshraj]

🚀 The feature

Requested by a user on slack:

https://embedchain.slack.com/archives/C05RG7CJKC6/p1704906334878579

Docs: https://community.openai.com/t/how-do-i-use-the-new-json-mode/475890

Motivation, pitch

Provide support for all features offered by OpenAI llms.

[Praj-17]

Hi is this implemented, yet? I would want to implement it if it is not done.

[hardik1408]

@deshraj can I try implementing this issue?