doc: added using teh vpn on nix

src/tutorials/skynet/connect_vpn.md

@@ -26,3 +26,47 @@
 
 [openfortivpn]: https://github.com/adrienverge/openfortivpn
 [windows-forticlient]: https://www.fortinet.com/support/product-downloads#vpn
+
+
+## Nix
+
+For folks who have [nix][nix] installed they can use.  
+Details on how to use it can be found on the [github].  
+
+If you have NixOS installed you can use the following module.  
+It makes use of ``Mome Manager`` to create the config file in ``$USDERNAME``'s home dir.  
+Using ``vpn up`` and ``vpn down`` to control the vpn.
+
+```nix
+/*
+Config for UL VPN.
+Opens a small browser to grab the cookie
+Use ``vpn up ul`` and ``vpn down ul``
+*/
+{inputs, ...}: {
+  # https://github.com/NixOS/nixpkgs/issues/231038#issuecomment-1637903456
+  environment.etc."ppp/options".text = "ipcp-accept-remote";
+
+  home-manager.users."$USDERNAME".home = {
+    file.".vpn".text = ''
+      [
+          {
+              "name": "ul",
+              "host": "ulssl.ul.ie",
+              "port": 443,
+              "default": true,
+              "cert": ""
+          }
+      ]
+    '';
+
+    packages = [
+      inputs.openfortivpn-cli.packages.x86_64-linux.default
+    ];
+  };
+}
+```
+
+
+[nix]: ../../skynet/nix.md
+[github]: https://github.com/adrienverge/openfortivpn