Refactor the `kotaemon/pipelines` module to `kotaemon/indices`. Create the VectorIndex.
Note: currently I place `qa` to be inside `kotaemon/indices` since at the moment we only have `qa` in RAG. At the same time, I think `qa` can be an independent module in `kotaemon/qa`. Since this can be changed later, I still go at the 1st option for now to observe if we can change it later.
* enforce Document as IO
* Separate rerankers, splitters and extractors (#85)
* partially refractor importing
* add text to embedding outputs
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Co-authored-by: Nguyen Trung Duc (john) <trungduc1992@gmail.com>
