GraphRAG support

[DuboisABB]

This issue is for a: (mark with an x)

- [ ] bug report -> please search issues before submitting
- [X] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)

I just recently learned about a new RAG approach called GraphRAG, which shows impressive improvements over plain RAG: https://data.world/blog/generative-ai-benchmark-increasing-the-accuracy-of-llms-in-the-enterprise-with-a-knowledge-graph/

Microsoft already has an accelerator project here: https://github.com/Azure-Samples/graphrag-accelerator

It would be nice if this new RAG approach could be integrated into this project, although I'm not sure if it's mature enough yet.