text: Title: Add tutorial notebook to docs.cleanlab.ai
  Body: Make tutorial notebook appear on docs.cleanlab.ai (and verify it looks good on the website) by adding it to:
  1) https://github.com/cleanlab/cleanlab/blob/master/docs/source/tutorials/index.rst
  2) https://github.com/cleanlab/cleanlab/blob/master/docs/source/index.rst