Instructions on project page may be outdated

The project page says:

The library's source can be installed directly in the subtheme directory by running `npm install` in that location. After doing this, you can set up your assets by copying them from node_modules/uswds/dist, and then running a basic npm script to compile the CSS.

However, I found that running `npm install` had no effect. I see "up to date, audited 1 package in 169ms". But node_modules is not created.