Forward zoo.wpcarro.dev connections to :8000

Right now the 8000 port is hard-coded into the zoo server, which isn't ideal,
but "it works" (TM).

default.nix

@@ -33,4 +33,5 @@ in {
   third_party  = readTree ./third_party;
   tools        = readTree ./tools;
   buildHaskell = readTree ./buildHaskell;
+  zoo          = readTree ./zoo;
 }