Add missing 'type', 'defaultText' and 'literalExample' in module definitions

- add missing types in module definitions
- add missing 'defaultText' in module definitions
- wrap example with 'literalExample' where necessary in module definitions

nixos/modules/services/misc/gitit.nix

@@ -35,6 +35,7 @@ let
       };
 
       haskellPackages = mkOption {
+        type = types.attrsOf types.package;
         default = pkgs.haskellPackages;
         defaultText = "pkgs.haskellPackages";
         example = literalExample "pkgs.haskell.packages.ghc784";