change package dir layout

flake.nix

@@ -14,7 +14,7 @@
           type = "app";
           program = "${drv}/${exePath}";
         };
-      mkPackage = pkgs: name: pkgs.callPackage ./packages/${name}.nix { };
+      mkPackage = pkgs: name: pkgs.callPackage ./packages/${name} { };
 
       defaultApp = builtins.head apps; # first app is default one
       packages = apps ++ nonApps;