holy shit, we have 3 new functions! `just` is a si...

# arrow

[pakoito]

holy shit, we have 3 new functions! just is a simple constructor for the success case, defined in Applicative. flatMap defines sequential execution, where we need to “receive” the value before we deserialize it, and it’s defined in Monad. raiseError is defined in MonadError and like just is a constructor but for errors