[3.14] gh-106318: Add examples for str.replace() method (GH-143581) (GH-143789)

(cherry picked from commit af9f783)

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

Author: miss-islington

Doc/library/stdtypes.rst

@@ -2512,6 +2512,14 @@ expression support in the :mod:`re` module).
    Return a copy of the string with all occurrences of substring *old* replaced by
    *new*.  If *count* is given, only the first *count* occurrences are replaced.
    If *count* is not specified or ``-1``, then all occurrences are replaced.
+   For example:
+
+   .. doctest::
+
+      >>> 'spam, spam, spam'.replace('spam', 'eggs')
+      'eggs, eggs, eggs'
+      >>> 'spam, spam, spam'.replace('spam', 'eggs', 1)
+      'eggs, spam, spam'
 
    .. versionchanged:: 3.13
       *count* is now supported as a keyword argument.