Sets or gets a range slider's step type.
Note: This property is only relevant when the sliderType is set to 'Stepped'.
The stepType defines the steps in a stepped range slider's track.
It can be set to one of the following:
'Number': The number of steps is determined by the step
property's value. For example, suppose a range slider has a min
value of 0, max value of 10, and step value
of 5. There will be 5 steps, meaning each step will be 2 units.

'Value': The value of each step is equal to the number of units defined by
the step property's value. For example, suppose a slider has
a min value of 0, max value of 10, and step
value of 5. Each step size will be 5 units, meaning there will be two 2 steps.
