Functions for Vector Stores

[TechedLemur]

Describe the feature or improvement you're requesting

The client is missing functions for creating/modifying Vector Stores, and uploading files to the Vector Stores.
Here is the OpenAI docs where they have examples with the Python and Node SDKs: https://platform.openai.com/docs/assistants/tools/file-search#step-2-upload-files-and-add-them-to-a-vector-store

Additional context

I think we can use the existing Files api for uploading the files, and then attach the file to the Vector Store with a simple POST requests afterwards.
Here is an article where someone uses CURL to create Vector Stores and upload files, it should be possible to use those requests as inspiration for the rust client functions: https://4sysops.com/archives/create-an-assistant-with-vector-store-using-the-openai-api-and-curl/