title: Prevent CSS duplication in Webpack chunks when using code split
body: <p>I'm on a projet using LESS imported from JS bundled by <code>webpack</code>4.</p>
  
  <p>My problem is that the project have its own design-system, with components using same components like "typography"</p>
  
  <p>Example:<br>
  I have a button that import <code>typo.less</code>.<br>
  So all my chunks using that button will generate the result of <code>typo.less</code>.<br>
  How can I prevent this duplication?
  <code>splitChunks</code> seems not to operate here.</p>