Add shell for Hugo development

shells/default.nix

@@ -2,4 +2,5 @@
 
 with pkgs; {
   flatpak = callPackage ./flatpak.nix { };
+  hugo = callPackage ./hugo.nix { };
 }

shells/hugo.nix

@@ -0,0 +1,11 @@
+# My usual toolchain for developing Hugo projects.
+{ mkShell, hugo, git, go, nodejs-16_x }:
+
+mkShell {
+  packages = [
+    hugo # The main tool.
+    go # I might use Go modules which requires the Golang runtime.
+    git # VCS of my choice.
+    nodejs-16_x # The supported NodeJS version.
+  ];
+}