Mentioned expected nixos version

Author: SuperSandro2000

README.md

@@ -10,8 +10,11 @@ A minimal root filesystem for running NixOS on the Windows Subsystem for Linux
 ## System requirements
 
 NixOS-WSL is tested with the Windows Store version of WSL 2, which is now available on all supported Windows releases (both 10 and 11).
+
 Support for older "inbox" versions is best-effort.
 
+The main branch is intended to be used with nixos-unstable. For stable please look at the corresponding tags.
+
 ## Quick start
 
 First, [download the latest release](https://github.com/nix-community/NixOS-WSL/releases/latest).