Looking over things, it seems that we may not have actually added such a feature to the game's options, so I'll see what we can do for the future.

For the time being, it may be possible to force vsync on/off via your graphics card driver settings. If you can let me know whether you have an AMD, Nvidia card, or Intel graphics card, I can try to find some guides (but no promises that it would work, driver level vysnc forcing has always been hit or miss for me).

Ok, good news, we're working on adding that in!