The stepper motor has been released in version 2.4.0. It requires a driver, like the A4988 or DRV8825. You can find the information here: https://blokdots.com/documentation/components/outputs/stepper-motor

The Grove motor driver should support a step motor. We will have to see, if we can expand to motor driver support in Johnny-Five to work with a step motor attached to the Grove driver. Unfortunately there's a few other things planned before we will look at the step motor.