Add nushell to shells
diff --git a/modules/shells.nix b/modules/shells.nix
new file mode 100644
index 0000000..7c5c28a
--- /dev/null
+++ b/modules/shells.nix
@@ -0,0 +1,3 @@
+{ pkgs, ... }: {
+  config.environment.shells = with pkgs; [ bashInteractive zsh nushell ];
+}