Added example for Dataframe.align
- [ ] closes #42125 
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry
@MarcoGorelli 
Soo, we use `blackdoc`for doc formatting right🤔? I was really confused between `black` n `blackdoc`.😕 > Soo, we use `blackdoc`for doc formatting rightthinking? I was really confused between `black` n `blackdoc`.confused

docstring are formatted with a custom check which runs flake8, but it doesn't autoformat them, that's something we need to do manually unfortunately. I'd like to make it automatic though, it's kinda on my todo list