Request: Auto skip main menu in X seconds for unattended Win 10 installation

[longpanda]

Currently Ventoy support VTOY_MENU_TIMEOUT & VTOY_DEFAULT_IMAGE
https://www.ventoy.net/en/plugin_control.html

This just auto boot one of these ISO files in the list. Maybe we can use special string to implement it.

For example, set VTOY_DEFAULT_IMAGE to "VTOY_BOOT_1ST_HDD"