feature: add dataloader to cache some requested data

[lowsky]

Dataloader library allows to cache requests which would normally lead to a huge "load",
Typical example:
loading the Twitter follower's followers which would lead to loading some followers more than one time, even while it was already fetched, e.g.
Follower X -> follows Y and
follower Y also follows X
-> here we want to optimize it to only fetch X and Y once.

See https://github.com/facebook/dataloader