shell: Add nix-update / rustscan

rustscan is a nice alternative to nmap that's easier to use and doesn't
require the usage of sudo in certain situations.

nix-update is a nice script that makes updating the versions and hashes
of packages way easier than editing them by hand.

modules/shell.nix

@@ -32,6 +32,7 @@ in
           timg
           choose
           sd
+          rustscan
           ;
         inherit (pkgs)
           treefmt
@@ -95,6 +96,7 @@ in
         inherit (pkgs)
           nixpkgs-review
           nix-init
+          nix-update
           statix
           nvd
           nix-search-cli