Demonstrate py --list in the quickstart section of the Windows doc page (GH-29383)

(cherry picked from commit 1ecfe3d)

Co-authored-by: Christian Clauss <[email protected]>

Author: miss-islington

Doc/using/windows.rst

@@ -716,6 +716,12 @@ If you see the following error, you do not have the launcher installed:
 Per-user installations of Python do not add the launcher to :envvar:`PATH`
 unless the option was selected on installation.
 
+::
+
+  py --list
+
+You should see the currently installed versions of Python.
+
 Virtual environments
 ^^^^^^^^^^^^^^^^^^^^