Add virtualisation.vmVariantWithDisko option

docs/interactive-vm.md

@@ -12,6 +12,16 @@ afterwards you can run the interactive VM with:
 result/bin/disko-vm
 ```
 
+You can configure the VM using the `virtualisation.vmVariantWithDisko` NixOS option:
+
+```nix
+{
+  virtualisation.vmVariantWithDisko = {
+    virtualisation.fileSystems."/persist".neededForBoot = true;
+  };
+}
+```
+
 extraConfig that is set in disko.tests.extraConfig is also applied to the interactive VMs.
 imageSize of the VMs will be determined by the imageSize in the disk type in your disko config.
 memorySize is set by disko.memSize