added README

system/user.nix

@@ -1,6 +1,7 @@
 {
   pkgs,
   myConfig,
+  config,
   ...
 }: {
   users = {
@@ -8,6 +9,7 @@
       ${myConfig.nixos.username} = {
         isNormalUser = true;
         extraGroups = ["wheel" "networkmanager" "input" "video"];
+        hashedPasswordFile = config.sops.secrets.default_password.path; # FIXME: may not work!
         useDefaultShell = true;
       };
     };