asRetriever options any

I don't really do much work on the TS library, but my guess from the python perspective is that asRetriever() is on the base index class

As such, the options are specific to the subclass, but they all share that base method, so the options are generic

If you want to see the actual options, check out the actual retriever class (VectorIndexRetriever in this case)

Let me check it up I’ll circle back

I might have a PR.