Need to document requirements for Milvus integration

[andrewrfreed]

In this example, we use Milvus to search a document collection that we previously indexed with this python script. We include this script as an example for reference.

requirements.txt would be great, I needed to run:

pip install PyPDF2
pip install langchain
pip install huggingface_hub
pip install pymilvus

[jwm4]

@mdswift completed this and also clarified the distinction between the REST and gRPC ports for Milvus (because the extension uses the former and the ingestion program uses the latter).