gh-106318: Add doctest role and a 'See also' to the str.split() docs (GH-144367)

(cherry picked from commit a96cba5)

Co-authored-by: Adorilson Bezerra <adorilson@gmail.com>

Author: adorilson

Doc/library/stdtypes.rst

@@ -2461,7 +2461,9 @@ expression support in the :mod:`re` module).
    :func:`re.split`). Splitting an empty string with a specified separator
    returns ``['']``.
 
-   For example::
+   For example:
+
+   .. doctest::
 
       >>> '1,2,3'.split(',')
       ['1', '2', '3']
@@ -2479,7 +2481,9 @@ expression support in the :mod:`re` module).
    string or a string consisting of just whitespace with a ``None`` separator
    returns ``[]``.
 
-   For example::
+   For example:
+
+   .. doctest::
 
       >>> '1 2 3'.split()
       ['1', '2', '3']
@@ -2491,7 +2495,9 @@ expression support in the :mod:`re` module).
    If *sep* is not specified or is ``None`` and  *maxsplit* is ``0``, only
    leading runs of consecutive whitespace are considered.
 
-   For example::
+   For example:
+
+   .. doctest::
 
       >>> "".split(None, 0)
       []
@@ -2500,7 +2506,7 @@ expression support in the :mod:`re` module).
       >>> "   foo   ".split(maxsplit=0)
       ['foo   ']
 
-   See also :meth:`join`.
+   See also :meth:`join` and :meth:`rsplit`.
 
 
 .. index::