adding suggested code to get the two latest nixos releses

quickget

@@ -906,7 +906,8 @@ function releases_nitrux() {
 }
 
 function releases_nixos() {
-    echo unstable 24.05 23.11 23.05
+    # unstable plus the two most recent releases
+    echo unstable $(web_pipe https://nix-channels.s3.amazonaws.com/?delimiter=/ | grep -o -P '(?<=<Key>nixos-)[0-9]+.[0-9]+(?=</Key>)' | sort -nr | head -n +2)
 }
 
 function editions_nixos() {