Use boilerplate/typescript for goals

After deploying the version of this application that built everything in the
browser, which originally was the impetus for the entire project, I learned that
the babel in-browser transformer won't work. I'm not sure why, but I need to
move on from this project and do other work.

I ported the code to my boilerplate/typescript, which works. Wahoo!

website/goals/shell.nix

@@ -3,5 +3,6 @@ let
 in pkgs.mkShell {
   buildInputs = with pkgs; [
     nodejs
+    yarn
   ];
 }