Add discussion of doctesting interactive code examples.

There have been various discussions about doctesting interactive code examples in the python docs. The consensus has been that it is desirable that they pass. Indeed, CI currently has a (pass-not-required) Tests / Docs / Doctest. (But it seems to be setup to be excessively lenient, passing many errors that are normally caught. Intended? Bug?) There has been additional discussion about use of particular features, such as doctest directives. An example from the doc:

The [ELLIPSIS](https://docs.python.org/3/library/doctest.html#doctest.ELLIPSIS) directive
gives a nice approach for the last example:
>>> C()  # doctest: +ELLIPSIS
<C object at 0x...>

Other people may remember such discussions better. In any case, a summary of current policy should be added either in
Documentation / Style Guide /Code Examples or in a new "Interactive Code Examples and Doctest" section immediately after.

Lee Documentation/Style Guide/Code Examples y la documentación de doctest, especialmente los ejemplos interactivos y las indicaciones sobre directivas. Revisa la comprobación de Docs/Doctest CI y las discusiones mencionadas para establecer la política actual; después, añade un resumen conciso en la sección existente o en una sección nueva inmediatamente a continuación. La tarea estará terminada cuando la guía explique el comportamiento esperado de doctest y las directivas relevantes para los ejemplos interactivos.