Humidifiers produce steam.
Anything dissolved in the water does not become part of the steam.
Steam is pure water vapour, nothing more, nothing less.
So, unless you want to disinfect your humidifier, adding it to the water will not do anything for your plants or your grow space - good or bad.
It will however leave residue in your humidifier, which could cause issues with its workings, so why do it?