vm: Serve www directory from a shared directory

Run the VM as

    WWW="$PWD/www" nix run

to serve the www directory from within the VM.

module.nix

@@ -6,7 +6,7 @@
       virtualHosts.localhost.locations."/" = {
         index = "index.html";
 
-        root = ./www;
+        root = "/var/www";
       };
     };
   };
@@ -19,5 +19,10 @@
     host.port = 8080;
   }];
 
+  virtualisation.sharedDirectories.www = {
+    source = "$WWW";
+    target = "/var/www";
+  };
+
   system.stateVersion = "23.11";
 }