add flakes commands to everything

hosts/profiles/core/default.nix

@@ -20,6 +20,7 @@ in
       allowed-users = [ "@wheel" ];
       auto-optimise-store = true;
       system-features = [ "nixos-test" "benchmark" "big-parallel" "kvm" ];
+      experimental-features = [ "nix-command" "flakes" ];
     };
     gc.automatic = true;
     optimise.automatic = true;