Hi, folks. Shouldn't we have a `lift` for the Bifu...

# arrow-contributors

[Leandro Borges Ferreira]

Hi, folks. Shouldn't we have a lift for the Bifunctor class? I noticed that it doesn't have it. It could be just like this:

interface Bifunctor<F> {
    fun <A, B, C, D> Kind2<F, A, B>.bimap(fl: (A) -> C, fr: (B) -> D): Kind2<F, C, D>

    fun <A, B, C, D> lift(fl: (A) -> C, fr: (B) -> D): (Kind2<F, A, B>) -> Kind2<F, C, D> = { kind2 ->
        kind2.bimap(fl, fr)
    }
// more code...

If it makes sense, I'll open a PR