Document how to plot figures in generated docs from docstrings
Follow up for #20015. We need to write documentation about how to do this using blocks like:
```
..plot:: 
    :context: close-figs
    >>> s = pd.Series([1, 3, 2])
    >>> s.plot.line()
```

Should this be part of https://pandas.pydata.org/pandas-docs/stable/contributing.html#contributing-to-the-documentation? Are we planning to move the contents of https://python-sprints.github.io/pandas/guide/pandas_docstring.html there in a close future?
