Add a shortcut to resolve the issue where Windows 11 on an Ubuntu 26.04 virtual machine cannot use the split-screen mode

[Tianyazi]

On Ubuntu budgie 26.04 (Wayland) with VBox 7.2.16 (Windows 11), screen splitting is not possible, However,
on Ubuntu budgie 24.04 (X11) with VBox 7.2.16 (Windows 11), screen splitting is available,
It is recommended to add a send shortcut here to easily resolve the screen split issue.
win+➡
win+⬅