DOC: add example to reorder levels
- [ x] closes #42124
- [ ] tests added / passed
- [x ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ x] whatsnew entry - Included example for reorder_levels

Hello @prabha-git! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2021-06-25 23:10:03 UTC closing for now as stale, thanks anyway for your PR!