Copy examples directory into website directory on deploy

Currently, in the root directory of this project, are directories `examples` and `website`. The `examples` directory contains some examples of TextureMap being used with different geometry types. The `website` directory contains the website, which is the only part of the repository that is deployed by Netlify.

I think this structure for the project makes sense in terms of discoverability: `examples` in the root makes it easier to find. However, it would be handy to be able to publish these on the website so they'd appear at https://texturemap.org/examples.

Have we ever written a script like this on Netlify? I [took a shot](https://github.com/azavea/texturemap/blob/master/src/copy-examples.js) but couldn't get it work.