[Feature request] Icon for submenu

[longpanda]

In fact, there is class defined for these sub menu and I just haven't had time to update the document in the website.

For example, see  https://github.com/ventoy/Ventoy/blob/ma.../power.cfg

Code:

menuentry Reboot --class=power_reboot {
    echo -e '\n\nSystem is rebooting ... \n'
    sleep 1
    reboot
}

menuentry Halt --class=power_halt {
    echo -e '\n\nSystem is halting ... \n'
    sleep 1
    halt
}

menuentry 'Return to menu [Esc]' --class=vtoyret VTOY_RET {
    echo 'Return ...'
}

--class=xxx is the class defination.

power_reboot  power_halt  are the corresponding class and you just need to prepare a power_reboot.png  and power_halt.png