Add note about README into the source files

Author: anttih

src/Partial.purs

@@ -1,5 +1,5 @@
--- | Some partial helper functions.
-module Partial 
+-- | Some partial helper functions. See the README for more documentation.
+module Partial
   ( crash
   , crashWith
   ) where

src/Partial/Unsafe.purs

@@ -1,4 +1,5 @@
 -- | Utilities for working with partial functions.
+-- | See the README for more documentation.
 module Partial.Unsafe
   ( unsafePartial
   , unsafePartialBecause