Add types for PIL.ImageTk (#9733)

stubs/Pillow/@tests/test_cases/check_tk_compat.py

@@ -0,0 +1,15 @@
+# Verify that ImageTK images are valid to pass to TK code.
+from __future__ import annotations
+
+import tkinter
+
+from PIL import ImageTk
+
+photo = ImageTk.PhotoImage()
+bitmap = ImageTk.BitmapImage()
+
+tkinter.Label(image=photo)
+tkinter.Label(image=bitmap)
+
+tkinter.Label().configure(image=photo)
+tkinter.Label().configure(image=bitmap)