feat: add lib as overlay

overlays/default.nix

@@ -5,4 +5,5 @@ lib.composeManyExtensions [
   (import ./packages.nix { inherit inputs lib; })
   (import ./vimPlugins.nix { inherit inputs lib; })
   (import ./wayland.nix { inherit inputs lib; })
+  (import ./lib.nix { inherit inputs lib; })
 ]

overlays/lib.nix

@@ -0,0 +1,5 @@
+{ lib, inputs }:
+
+final: prev: {
+  inherit lib;
+}