add swap size param

base.nix

@@ -19,13 +19,19 @@ in {
       example = "example@example.com";
       description = "Email of the admin, use for ACME and stuff";
     };
+    swapSize = mkOption {
+      type = types.int;
+      default = 1024;
+      example = 2048;
+      description = "Size of the swap file";
+    };
   };
   config = {
     swapDevices = [
       {
         device = "/swapfile";
         priority = 0;
-        size = 1024;
+        size = cfg.swapSize;
       }
     ];