[FEATURE] Leverage code in LangChain and neo4j-graphrag, and have extensions to them to ease integration

[stevereiner]

What is the use case?

1. Save development time by leverage code in these libraries
2. Work into existing code using LangChain, leverage developer knowledge
3. Ensures that LangChain, etc query code will work with cocoindex
   Describe the solution you'd like
   1, Extend LangChain classes focused on embeddings, vector stores, graphs
4. Extend neo4j-graphrag (Apache 2.0 open source) extend for other graph databases (Kuzu, Arcade) In addition to KG build pipeline setup code, has vector, index, and embedding code although may be wrappers to LangChain or LangChain community parts for neo4j
   Additional context

---

❤️ Contributors, please refer to 📙Contributing Guide.
Unless the PR can be sent immediately (e.g. just a few lines of code), we recommend you to leave a comment on the issue like I'm working on it or Can I work on this issue? to avoid duplicating work. Our Discord server is always open and friendly.