DOC: there is no example for plotting asymmetrical errorbars
#### Location of the documentation

[errorbar visualization](https://pandas.pydata.org/pandas-docs/stable/user_guide/visualization.html#plotting-with-error-bars)

#### Documentation problem

Currently there's only an example of the symmetrical case, i.e. where the lower/upper errors are the same. The asymmetrical case is supported but actually quite tricky to get to work. I could only find one [stackoverflow post](https://stackoverflow.com/questions/45798492/asymmetrical-errorbar-with-pandas) and it is not especially helpful

#### Suggested fix for documentation

I suggest adding an example that showcases how to plot asymmetrical errorbars
