gh-92727: Add example of named group in doc for re.Match.__getitem__ (GH-92730)

(cherry picked from commit 642d1fa8)

Co-authored-by: Baptiste Mispelon <bmispelon@gmail.com>

Doc/library/re.rst

@@ -1324,6 +1324,14 @@ Match objects support the following methods and attributes:
       >>> m[2]       # The second parenthesized subgroup.
       'Newton'
 
+   Named groups are supported as well::
+
+      >>> m = re.match(r"(?P<first_name>\w+) (?P<last_name>\w+)", "Isaac Newton")
+      >>> m['first_name']
+      'Isaac'
+      >>> m['last_name']
+      'Newton'
+
    .. versionadded:: 3.6