Support third-party openai api provider

[Wanxp]

Thank you develop this plugins. please help add support for third-party openai api.

[sammcj]

Came here to log this same ticket!

Would be great to see Ollama as a provider, or if that's not possible to be able to provide a custom OpenAI compatible API endpoint and model.

[nanhuayu]

@sammcj @Wanxp I've introduced a base URL option in the ChatGPT interface to enhance flexibility and enable users to specify their own endpoint. I hope the author considers merging this feature into the main branch for broader utility. Added base url