feat(njord): add signing commit tool

modules/hosts/njord/configuration.nix

···
     ];
 
     homebrew.casks = [
-      "amethyst"        # Window manager
-      "discord"         # Discord client - used instead of the nix one for krisp
-      "figma"           # Collaborative design application
-      "zed"             # Code editor
-      "logi-options+"   #
+      "amethyst"            # Window manager
+      "discord"             # Discord client - used instead of the nix one for krisp
+      "figma"               # Collaborative design application
+      "gpg-suite-no-mail"   # Signing tool for commits
+      "logi-options+"       #
+      "zed"                 # Code editor
     ];
   };
 in