move nh config to module

modules/nix/nh.nix

@@ -0,0 +1,9 @@
+{ config, lib, pkgs, ...}:
+{
+programs.nh = {
+    enable = true;
+    clean.enable = true;
+    clean.extraArgs = "--keep-since 30d --keep 10";
+    flake = "/home/smayzy/nix-config";
+  };
+}