Add sandbox project using Contentful CMS

I used the boilerplate/typescript project as a starting point. This project
fetches and renders books that I'm defining in a Contentful CMS that I created.

website/sandbox/contentful/default.nix

@@ -0,0 +1,19 @@
+let
+  pkgs = import <nixpkgs> {};
+in pkgs.stdenv.mkDerivation {
+  name = "ideal-website";
+  srcs = ./.;
+  buildInputs = with pkgs; [
+    nodejs
+    # Exposes lscpu for parcel.js
+    utillinux
+  ];
+  # parcel.js needs number of CPUs
+  PARCEL_WORKERS = "1";
+  buildPhase = ''
+    npx parcel build index.html
+  '';
+  installPhase = ''
+    mv dist $out
+  '';
+}