Describes how to align the child along the axis that sizeFactor is modifying.
A value of -1.0 indicates the top when axis is Axis.vertical, and the start when axis is Axis.horizontal. The start is on the left when the text direction in effect is TextDirection.ltr and on the right when it is TextDirection.rtl.
A value of 1.0 indicates the bottom or end, depending upon the axis.
A value of 0.0 (the default) indicates the center for either axis value.
final double axisAlignment;