Fix atomWithEffectsFromRecoilValue effect onSet params

[barodeur]

First of all, thanks for this library 🙏.

I noticed that the ~newValue and ~oldValue parameters of the onSet effect callback had the type Recoil.t<'value> instead of 'value when using the FromRecoilValue function.

[bloodyowl]

Hi! Thanks for your PR!

Indeed that seems like a mistake.

Can you add a small test for onSet so that we confirm there won't be any regressions?