spacer method
Add spacer between every row in a table
Implementation
List<TableRow> spacer(double size) {
if (length < 2) return this;
final factor = first.children.length;
final spacer = TableRow(children: List.generate(factor, (_) => SizedBox(height: size)));
return [
for (int i = 0; i < length; i++) ...[this[i], if (i < length - 1) spacer],
];
}