text: Title: JS - Right bar navigation
  Body: The [docs](https://ploomber.readthedocs.io/en/latest/user-guide/deployment.html) have a right bar that shows the contents of the current article
  
  ![Screen Shot 2021-10-15 at 12 24 27](https://user-images.githubusercontent.com/989250/137522983-6d25c30f-db27-462a-b7a0-a74be5b20ee8.png)
  
  The font-weight should change to highlight the current section but it's no longer working, I'm not sure why:
  
  here's the JS code: https://github.com/ploomber/ploomber/blob/master/doc/_static/js/custom.js
  
  check out doc/contributing.md for details