parallel compression and decompression

I've selected a chunk size of 8000 bytes rather arbitrarily, but it
seems to work just fine. The bigger problem is that the simplified
final fraction makes the running fraction in decompression's foldl
more complicated as time goes on, making it around 50 times slower
than compression. It takes just under an hour to decompress the
Great Gatsby.

compress.cabal

@@ -53,7 +53,9 @@ executable compress
     optparse-generic,
     vector,
     nonempty-containers,
-    primes
+    witch,
+    monad-par,
+    monad-par-extras
   default-language:
     GHC2021
   other-modules:
@@ -63,8 +65,9 @@ executable compress
      Compress.PrefixTree
      Data.HuffmanTree
      Compress.Arithmetic
+     Data.WordyMap
   ghc-options:
     -threaded
     -fprof-auto
     -fprof-late
-    "-with-rtsopts=-p -hc"
+    "-with-rtsopts=-p -hc -B -N -qa"