title: What is the role of package.json fields "sass" and "style"?
body: <p>There is bootstrap 4 package.json
  <a href="https://github.com/twbs/bootstrap/blob/v4-dev/package.json" rel="nofollow noreferrer">https://github.com/twbs/bootstrap/blob/v4-dev/package.json</a></p>
  
  <p>There are several interesting fields <code>style</code> and <code>sass</code> (unknown for me)</p>
  
  <pre><code>{
    //...
    "style": "dist/css/bootstrap.css",
    "sass": "scss/bootstrap.scss",
    "main": "dist/js/bootstrap",
    //...
  }
  </code></pre>
  
  <p>Since they precede the highly important <code>main</code> field I start thinking that they are also very important. Can you advice on their role? I'm sure that <code>node-sass</code> works without them so which tool is a target?</p>