Support for Pinecone Hybrid Search (Sparse-dense embeddings)
I have found that the OpenAI embeddings are decent, but suffer when you want specific names or keywords to be included. I've found that the [sparse-dense approach](https://www.pinecone.io/learn/sparse-dense) produces better results, but not supported by the current implementation of the Vectorstore or the chains. 

Has anyone else implemented a workaround or is there any planned support for this?