[FEATURE] Support GraphRAG using Neo4j

[stephanj]

The current RAG implementation could really benefit from an additional GraphRAG feature as explained by Michael Hunger at Devoxx Belgium.

https://www.youtube.com/watch?v=kRqJXDLRbRE

We can pull image from Docker and have it run similarly like ChromaDB from https://hub.docker.com/_/neo4j

Langchain4J supports Neo4J, example @ https://github.com/langchain4j/langchain4j/tree/main/langchain4j-neo4j
Neo4J example @ https://neo4j.com/labs/genai-ecosystem/langchain4j/

We would reuse the existing Nomic embedding.

[stephanj]

Making progress, basically swapping ChromaDB with Neo4J Graph & similarity search on AST data 🤩🔥🔥🔥

Demo @ https://www.youtube.com/watch?v=PCREFuF_1-0