add default.nix

default.nix

+{ mkDerivation, aeson, aeson-pretty, base, bytestring
+, bytestring-encoding, containers, either, extra, filepath
+, getopt-generics, lib, mtl, regex-tdfa, text, transformers, vector
+}:
+mkDerivation {
+  pname = "walint";
+  version = "0.1.0.0";
+  src = ./.;
+  isLibrary = true;
+  isExecutable = true;
+  libraryHaskellDepends = [
+    aeson base bytestring containers either extra filepath
+    getopt-generics mtl regex-tdfa text transformers vector
+  ];
+  executableHaskellDepends = [
+    aeson aeson-pretty base bytestring bytestring-encoding
+    getopt-generics text
+  ];
+  license = "unknown";
+  hydraPlatforms = lib.platforms.none;
+}