Add a langchain wrapper

[vmesel]

Hey folks! I would love to use weavel in a daily basis in work and some side projects that I work for, but I find the API too complicated to be integrated into Langchain's LCEL.

Are you guys open for a collab on this?

[aschung01]

Hey @vmesel, we don't have enough bandwith to work on the integration right now, but if you have the time to contribute we'd love to collaborate!