feat: Suggest follow up questions based on uploaded documents

[hiro-v]

Problem

• Similar feature in ChatPDF, after document ingested/ a query got answered, 3 suggested document will show up

Success Criteria

• After document ingested, call a request to LLM with a template as in https://github.com/langchain-ai/langchainjs/blob/main/examples/src/use_cases/advanced/conversational_qa.ts#L62 to generate follow up question
• After a query answered by LLM, send a request again to generate next possible question based on conversation history.

Additional context
Add any other context or screenshots about the feature request here.

[0xgokuz]

@hiro-v as discussed, let me write all the clarifications about this task here:

We want this feature to be there, regardless whether we're uploading a PDF document, or not. So I'm suggesting to break this task into 2 parts:

1. without PDF - the general feature, using a staric list of questions that is picked randomly
2. with PDF - using the PDF for the set of suggested questions to asks

anything else that I missed?

[0xSage]

closing as dupe of janhq/cortex.cpp#1595