Support OpenAI API format

[anagri]

Support OpenAI API format by giving option to switch between Ollama proprietary API format and OpenAI API format.

To fetch list of models - https://platform.openai.com/docs/api-reference/models/list?lang=node.js

To generate chat - https://platform.openai.com/docs/api-reference/chat?lang=node.js

Will help servers following OpenAI API format be used with Hollama. E.g. Bodhi App - https://github.com/BodhiSearch/BodhiApp