Add type family `T`

[L-as]

type family T :: forall (edsl :: EDSLKind).  EType -> Type
type family T a where
  T @edsl a = Term edsl a

This is useful for annotating types inside terms

[L-as]

An alternative:

phe :: forall a edsl. Term edsl a -> Term edsl a
phe = id

x :: PConstructable edsl PBool => Term edsl PBool
x = phe @PBool $ pcon ETrue 

[L-as]

Fixed