Make this an overlay flake

default.nix

@@ -1,6 +1,6 @@
-self: super:
-with self;
-with self.lib;
+final: prev:
+with final;
+with final.lib;
 let
   mapAttrs = super.stdenv.lib.mapAttrs;
   flip = super.stdenv.lib.flip;

flake.nix

@@ -0,0 +1,5 @@
+{
+  outputs = { ... }: {
+    overlay = import ./default.nix;
+  };
+}