Create Nix package expressions (#1246)

nix/overlay.nix

@@ -0,0 +1,18 @@
+# You can use this file as a nixpkgs overlay. This is useful in the
+# case where you don't want to add the whole NUR namespace to your
+# configuration.
+
+self: super:
+
+let
+
+  isReserved = n: n == "lib" || n == "overlays" || n == "modules";
+  nameValuePair = n: v: { name = n; value = v; };
+  nurAttrs = import ./default.nix { pkgs = super; };
+
+in
+
+  builtins.listToAttrs
+  (map (n: nameValuePair n nurAttrs.${n})
+  (builtins.filter (n: !isReserved n)
+  (builtins.attrNames nurAttrs)))