semigroupoids: instance Alt Identity

[Gurkenglas]

I am currently making a typeclass that relates Alternatives and Alts that are differing by their empty for laziness and profit. Maybe belongs to Identity, but Identity doesn't have an Alt instance yet. It should have one, where (<!>) = const.

[neongreen]

I have asked Edward in #haskell-lens whether such an instance would make sense – waiting for a response.