Problem
Currently it is more complicated handling sse output from custom remote inference engines that do not follow the OpenAI spec

Success Criteria
Ability to transform the response similar to how "transformResponse" is used in non streaming cases

Additional context
Perhaps a function could be passed and used around this line to customise how an sse chunk is handled

https://github.com/janhq/jan/blob/0bad1a479f642c8c5183017641656d52c4b33c61/core/src/browser/extensions/engines/helpers/sse.ts#L74