nixos-vm: First proxy work

hosts/nixos-test/configuration.nix

@@ -31,7 +31,10 @@
     # following configuration is added only when building VM with build-vm
     virtualisation = {
       memorySize = 8192; # Use 8192MiB memory.
-      cores = 8;         
+      cores = 8;
+      forwardPorts = [
+        { from = "host"; host.port = 8888; guest.port = 80; }
+      ];
     };
   };
 
@@ -63,4 +66,6 @@
       };
     };
   };
+
+  networking.firewall.allowedTCPPorts = [ 80 ]; # Opens port 80 for HTTP traffic.
 }