Tutorials for new Composable Windows API (#721)

README.md

tutorials/Tray_Notifications_MenuBar/README.md

tutorials/Tray_Notifications_MenuBar_new/README.md

tutorials/Tray_Notifications_MenuBar_new/tray.gif

tutorials/Tray_Notifications_MenuBar_new/window_menubar.gif

tutorials/Window_API/README.md

tutorials/Window_API_new/README.md

tutorials/Window_API_new/ask_to_close.gif

tutorials/Window_API_new/hide_instead_of_close.gif

tutorials/Window_API_new/multiple_windows.gif

tutorials/Window_API_new/state.gif

tutorials/Window_API_new/window_properties.gif

tutorials/Window_API_new/window_splash.gif