add serial port device in usb presentation to host

[milangupta1]

For controlling servers without built-in graphics chipsets/cards, the display/console terminal is a rs232 serial port typically configured to run getty (linux). See :
https://unix.stackexchange.com/questions/726107/how-use-a-usb-rather-than-a-rs-232-port-as-a-text-terminal-connection-i-hope#:~:text=The%20rule%20could%20be%20put,See%20also%20this%20answer.&text=or%20whatever%20speed%20you%20want,to%2Dserial%20adapter%20supports%20it.

The kvm already presents itself as a keyboard, mouse and storage device. Would be amazing if it also presented itself as an optional rs232 serial port. This is likely a non-trivial feature as the port traffic would need to rendered as such in the UI as a serial terminal vs hdmi traffic renderer ...

Just dreaming .. the device is amazing either way ! Well done !