[3.8] bpo-41841: Prepare IDLE NEWS for 3.8.8 (GH-24344)

Author: terryjreedy

Lib/idlelib/NEWS.txt

@@ -1,5 +1,5 @@
-What's New in IDLE 3.8.7
-Released on 2020-12-??
+What's New in IDLE 3.8.8
+Released on 2021-02-15?
 ======================================
 
 
@@ -12,6 +12,10 @@ bpo-42508: Keep IDLE running on macOS.  Remove obsolete workaround
 that prevented running files with shortcuts when using new universal2
 installers built on macOS 11.
 
+What's New in IDLE 3.8.7
+Released on 2020-12-27
+======================================
+
 bpo-42426: Fix reporting offset of the RE error in searchengine.
 
 bpo-42416: Get docstrings for IDLE calltips more often