[3.8] bpo-41841: prepare for 3.8.9 (GH-24635)

Author: terryjreedy

Lib/idlelib/NEWS.txt

@@ -1,12 +1,16 @@
-What's New in IDLE 3.8.8
-Released on 2021-02-15?
-======================================
+What's New in IDLE 3.8.9
+Released on 2021-05-03?
+=========================
 
 
 bpo-43283: Document why printing to IDLE's Shell is often slower than
 printing to a system terminal and that it can be made faster by
 pre-formatting a single string before printing.
 
+What's New in IDLE 3.8.8
+Released on 2021-02-19
+======================================
+
 bpo-23544: Disable Debug=>Stack Viewer when user code is running or
 Debugger is active, to prevent hang or crash.  Patch by Zackery Spytz.