I just installed the latest Node.js on a clean system and get the same errors. Disregarding that, I do find the Library in there.
You should be able to find them in the directory_you_were_in\node_modules\spark path. Depending on what you want to do, you might not even need them like that. You can use the CDN to include the minified library into your webpage, if that’s what you’re making.
I also installed the latest Chrome version in which I do see the button. Not sure what’s going on there. Works in Edge, Chrome, Opera, (mobile) Safari at first glance. Haven’t tried others as of yet. The code is on GitHub as well, Should you find that easier.