gh-89610: Add .pyi as a recognised extension for IDLE on macOS (#95393)

This allows opening stub files by double clicking on them in the Finder.

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Lib/idlelib/NEWS.txt

@@ -3,6 +3,8 @@ What's New in IDLE 3.11.0
 Released on 2022-10-03
 =========================
 
+gh-89610: Add .pyi as a recognized extension for IDLE on macOS.  This allows
+opening stub files by double clicking on them in the Finder.
 
 bpo-28950: Apply IDLE syntax highlighting to `.pyi` files.  Add util.py
 for common components.  Patch by Alex Waygood and Terry Jan Reedy.

Mac/IDLE/IDLE.app/Contents/Info.plist

@@ -10,6 +10,7 @@
 			<key>CFBundleTypeExtensions</key>
 			<array>
 				<string>py</string>
+				<string>pyi</string>
 				<string>pyw</string>
 			</array>
 			<key>CFBundleTypeIconFile</key>

Misc/NEWS.d/next/IDLE/2022-07-28-18-56-57.gh-issue-89610.hcosiM.rst

+Add .pyi as a recognized extension for IDLE on macOS.    This allows opening
+stub files by double clicking on them in the Finder.