Support -- ^ comment style

[parsonsmatt]

Currently, you must use the -- | comment style for documenting fields and entities. This is not idiomatic Haskell, and folks often want to use -- ^ for documenting fields.

Related to #1296

Right now, you need to document like this:

-- | A table
SomeTable
    -- | Some Field
    someField Text

Ideally, we would be able to document like this:

-- | A table
SomeTable
    someField Text 
    -- ^ Some Field

Supporting same-line comments seems useful too.

SomeTable
    someField Text -- ^ This is a doc comment.

It seems less obvious that documenting entities like this makes sense. I've never see this on a Haskell datatype and I'm not sure it's even valid syntax.

SomeTable
    someField Text -- ^ Doc Comment
-- ^ I am a doc comment for SomeTable?? Weird.