Document import `hiding` keyword

[lucianojoublanc-da]

In the docs https://docs.daml.com/daml/reference/packages.html, the hiding keyword should be documented. e.g.

import DA.Next.Map 
import DA.List hiding (lookup)
import DA.Optional
import Prelude hiding (lookup)

[ruthwikchikoti]

@hurryabit @lucianojoublanc-da @basvangijzel-DA can i work on this