The Chart series extremes configuration. Applies to extreme outliers.
For more information, refer to
The background color of the series outliers.
The border of the extremes.
The rotation angle of the extremes.
The extremes size in pixels.
The extremes shape.
The supported values are:
"circle"—The marker shape is a circle.
"square"—The marker shape is a square.
"triangle"—The marker shape is a triangle.
"cross"—The marker shape is a cross.