Add Contravariance

Add contravariant functor i.e.:
```
λ(f : Type → Type)
→ { contra = ∀(a : Type) → ∀(b : Type) → (b → a) → f a → f b }
```

Should probably go under `Contravariant/Functor/Type`

Along with this we could add `Coyoneda` and other functionality.