DOC: Examples added for different types of plots in visualizations user guide
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

You have several unrelated changes to what the title of the PR says, including an added file I don't think we want to get it merged.

Also, afaik we don't use seaborn anywhere in the documentation, and it's not a dependency of pandas, so using seaborn would require discussion.

Closing this for now, please open an issue if you want to discuss using seaborn in examples, and feel free to open a new PR, but just add the related changes.