add example with app icon

example_004.py

@@ -0,0 +1,11 @@
+# example_004.py
+from tkinter import Tk, Image
+
+def main():
+    root = Tk()
+    icon = Image('photo', file='icon.png')
+    root.wm_iconphoto(True, icon)
+    root.mainloop()
+
+if __name__ == '__main__':
+    main()