Import css from npm module in rails with webpacker

I use highlight.js

In `app/javascripts/styles.js`

```js
import 'highlight.js/styles/github.css';
```

And then add to layout

```erb
<%= stylesheet_pack_tag 'styles' %>
```

Done.

You can simply replace highlight.js with any other module like bootstrap though

https://github.com/rails/webpacker/blob/master/docs/css.md