Mention @jwiegley's `parsec-free` package as debugging alternative

re #63

src/Text/Parsec.hs

@@ -83,6 +83,11 @@ module Text.Parsec
     , incSourceLine, incSourceColumn
     , setSourceLine, setSourceColumn, setSourceName
      -- * Debugging
+     --
+     -- | As a more comprehensive alternative for debugging Parsec parsers,
+     -- there's also the [parsec-free](http://hackage.haskell.org/package/parsec-free)
+     -- package.
+     --
     , parserTrace, parserTraced
      -- * Low-level operations
     , manyAccum

src/Text/Parsec/Combinator.hs

@@ -31,6 +31,11 @@ module Text.Parsec.Combinator
     -- tricky combinators
     , manyTill, lookAhead, anyToken
     -- * Debugging
+    --
+    -- | As a more comprehensive alternative for debugging Parsec parsers,
+    -- there's also the [parsec-free](http://hackage.haskell.org/package/parsec-free)
+    -- package.
+    --
     , parserTrace, parserTraced
     ) where