alignment property Null safety
If this property is non-null, and the children, separated by spacing, fit within the available width, then the overflow bar will be as wide as possible. If the children do not fit within the available width, then this property is ignored and overflowAlignment applies instead.
If alignment is one of MainAxisAlignment.spaceAround, MainAxisAlignment.spaceBetween, or MainAxisAlignment.spaceEvenly, then the spacing parameter is only used to see if the horizontal layout will overflow.
Defaults to null.
final MainAxisAlignment? alignment;