feat: add weaviate adapter

[TimPietrusky]

Motivation

We want to be able to save data into a vector store. Using Weaviate is the logical choice, as it is open source, can run on own servers or via Weaviate Cloud Services. They also allow multiple ways to interact with the data and according to the docs, we can store millions of objects in Weaviate without a degradation in speed.

ToDo

• Search for a string, not only return all objects of a specific class

[TimPietrusky]

@pixelass Wouldn't it make sense to receive the credentials also via env-variables? Or is this something that we don't worry here, as this is something that the user has to implement if they want?

EDIT: I updated the example to use env-variables.

[TimPietrusky]

@pixelass added functionality to actually search by filter for search.

You can also get objects by className with searchObjects.

[TimPietrusky]

I updated the docs to improve some texts and removed a broken link.