added support for chat.completion to return sse response

[raja-jamwal]

Describe your changes

• I was trying to use gpt4all with continue.dev but continue.dev expects SSE responses.
• Added changes to return SSE response.
• Tested with the publically available version of continue.dev and postman to validate the SSE response.

see this issue
#2174

Issue ticket number and link

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• I have added thorough documentation for my code.
• I have tagged PR with relevant project labels. I acknowledge that a PR without labels may be dismissed.
• If this PR addresses a bug, I have provided both a screenshot/video of the original bug and the working solution.

Demo

Steps to Reproduce

• install continue.dev, set it up to use the existing local gpt4all server. Ask him something, it blanks out.
• Use this build to ask it something, and it'll respond.

Notes

[raja-jamwal]

@cebtenzzre Can I get a review on this?

[manyoso]

@cebtenzzre , please deal with this.

[lrq3000]

@cebtenzzre @manyoso Can someone please review this PR? It would be awesome to finally be able to use GPT4All in all OpenAI API compatible apps (eg, not just continuedev but also OpenInterpreter).