Don't highlight top-level-only keywords at different levels

[Hi-Angel]

The keywords being modified here only represented keywords when they are at the beginning of a line with optional whitespace.

At different levels these would represent valid record fields or other identifiers.

This was tested by adding the following code to a PureScript file:

type Foo = { type :: Int
           , module :: Int
           , import :: Int
           , data :: Int
           , class :: Int
           , newtype :: Int
           , instance :: Int
           }

…and checking that compilation succeeds.

[Hi-Angel]

upd: added instance.

[Hi-Angel]

@kritzcreek , ping?

[Hi-Angel]

ping