gh-99836: IDLE - update news.txt for 3.12 (#104444)

* gh-99836: IDLE 3.12 news.txt

* gh-99836: IDLE - update news.txt for 3.12

Author: terryjreedy

Lib/idlelib/NEWS.txt

@@ -1,9 +1,20 @@
+What's New in IDLE 3.12.0
+(since 3.11.0)
+Released on 2023-10-02
+=========================
+
+
+gh-88496 Fix IDLE test hang on macOS.
+
+gh-103314 Support sys.last_exc after exceptions in Shell.
+Patch by Irit Katriel.
+
+
 What's New in IDLE 3.11.0
 (since 3.10.0)
-Released on 2022-10-03
+Released on 2022-10-24
 =========================
 
-
 gh-97527: Fix a bug in the previous bugfix that caused IDLE to not
 start when run with 3.10.8, 3.12.0a1, and at least Microsoft Python
 3.10.2288.0 installed without the Lib/test package.  3.11.0 was never