Add Clippy

[koppor]

AKA "context-aware help"

Is there a possibilty to request some assitance in an existing library: "Dear JabRef, I want to to attach a file here - how can I do?" - You know, like Clippy, but in helpful. (I am not referring to Clippy in Action)

We have AI token management here - and also embedding features. With the support of Ruslan, it could be a nice "excercise" how to embed RAG into an application.