Include module level documentation in the IR

Currently documentation is available at the type level, but if you provide module level docs those are not reflected in the IR.

In the example below, the Bar module's docs will not be present in the IR.

```elm
module Sample.Bar exposing (..)

{-|The Bar module
# Section 1
This is section 1

# Section 2
This is section 2

-}

{-|The Bar type. -}
type Bar
= Snickers
| Twix
```