Apply a jitter effect for the rendered markers.
When plotting discrete values, a little random noise may help telling the points apart.
The jitter setting applies a random displacement of up to n axis units in either direction.
So for example on a horizontal X axis, setting the jitter.x to 0.24 will render
the point in a random position between 0.24 units to the left and 0.24 units
to the right of the true axis position.
On a category axis, setting it to 0.5 will fill up the bin and make the data appear continuous.
When rendered on top of a box plot or a column series,
a jitter value of 0.24 will correspond to the underlying series' default groupPadding and pointPadding settings.