Previous IDLE What's New issues, such as #90653 and #86012, start with instructions on the IDLE-specific aspects of the IDLE section of Doc/whatsnew/3.yy.rst. Put an expanded version in a new section of Lib/idlelib/README.txt.

I am closing the two issues above because I want to try instead creating a single issue for each batch of changes that is not attached to a code change issue.