title: Is it possible to include custom css in htmlwidgets for R and/or LeafletR?
body: <p>I'd like to make some style changes to my leaflet map. </p>
  
  <p>Is it possible to include </p>
  
  <ul>
  <li>style elements OR</li>
  <li>a custom path to a css file</li>
  </ul>
  
  <p>either via htmlwidgets for R or LeafletR? </p>
  
  <p>Best</p>