add getting started video 10: creating Node.js modules

Here's the 10th Getting Started video. If you'd like to review and comment, please feel free to!

https://www.youtube.com/watch?v=PmT9ALVIczg

Before merge, these must be done:
- [ ] @rod11 reviews
- [ ] @iarna reviews
- [ ] Lin smooths out vocals
- [ ] Lin adds text