gh-95491: Mention IDLE Issue project in Readme (GH-95750) (#95791)

(cherry picked from commit 63140b445e4a303df430b3d60c1cd4ef34f27c03)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
diff --git a/Lib/idlelib/README.txt b/Lib/idlelib/README.txt
index 779b51c..76aec58 100644
--- a/Lib/idlelib/README.txt
+++ b/Lib/idlelib/README.txt
@@ -280,3 +280,11 @@
 version file gets a different number of backports, it is easiest to
 make a separate PR for each file and label it with the backports
 needed.
+
+Github repository and issues
+----------------------------
+
+The CPython repository is https://github.com/python/cpython.  The
+IDLE Issues listing is https://github.com/orgs/python/projects/31.
+The main classification is by Topic, based on the IDLE menu.  View the
+topics list by clicking the [<]] button in the upper right.