根据子项的基线对它们的位置进行定位的widget
Baseline({
Key key,
@required this.baseline,
@required this.baselineType,
Widget child,
})baseline: 80.0,baselineType: TextBaseline.alphabetic,3.2.1 对齐字母字符的字形底部的水平线
baselineType: TextBaseline.alphabetic,3.2.2 对齐表意文字的水平线
baselineType: TextBaseline.ideographic,child: Text('你好 Flutter'),