bpo-28097: IDLE - Add Previous/Next History to Shell menu (GH-11325)

(cherry picked from commit c0381aaea4ad3e866bde70393c4f7efe9bcf3568)

Co-authored-by: Cheryl Sabella <cheryl.sabella@gmail.com>
diff --git a/Lib/idlelib/mainmenu.py b/Lib/idlelib/mainmenu.py
index 6081a5f..f834220 100644
--- a/Lib/idlelib/mainmenu.py
+++ b/Lib/idlelib/mainmenu.py
@@ -82,6 +82,9 @@
    ('_View Last Restart', '<<view-restart>>'),
    ('_Restart Shell', '<<restart-shell>>'),
    None,
+   ('_Previous History', '<<history-previous>>'),
+   ('_Next History', '<<history-next>>'),
+   None,
    ('_Interrupt Execution', '<<interrupt-execution>>'),
    ]),