added mosh package and module

nixos/mosh.nix

@@ -0,0 +1,21 @@
+{ pkgs, ... }:
+
+{
+  # programs.mosh = {
+  #   enable = true;
+  #   programs.mosh.openFirewall = false;
+  # };
+
+  # services.openssh = {
+  #   settings = {
+  #     PasswordAuthentication = false;
+  #     KbdInteractiveAuthentication = false;
+  #     PermitRootLogin = "no";
+  #     AllowUsers = [ "xnm" ];
+  #   };
+  # };
+
+  environment.systemPackages = with pkgs; [
+    mosh
+  ];
+}