Add key to run default program w 'nix run .#'

nix run takes the name of the derivation by default
As the binary is called hyprkeys, not Hyprkeys it was necessary to use 'nix shell .# -c hyprkeys'

nix/default.nix

@@ -10,11 +10,14 @@
         ];
       }
   ),
+  lib,
 }:
 pkgs.buildGoApplication {
   pname = "Hyprkeys";
   version = "1.0.0";
   pwd = ../.;
   src = ../.;
   modules = ./gomod2nix.toml;
+
+  meta = with lib; {mainProgram = "hyprkeys";};
 }