You can use an IoT relay that people here use to get on/off control of their spindle using the PWM or 0-10 volt output directly. That relay is specifically designed for what you want to do.
be careful with your IoT AC current draw, you may need to use two of them
No G-code changes needed. You can use the standard post processor.
Take a look at the first part of this thread.
Oops forgot the link
Link