Add GrammKit by following the directions here: https://github.com/NixOS/nixpkgs/tree/master/pkgs/development/node-packages

EDIT: Also note that following those directions results in a huge diff, perhaps that should be noted there so people know that it's normal (assuming it is).

This cannot be merged as is. @seagreen, if you still need this, could you rebase it or otherwise update it against master?

I'd still like to have GrammKit at some point, but it's not a priority for me at the moment so I'll close this.