ECharts tooltip 位置设置

Echarts如果data较多tooltip默认显示会遗漏一些数据，导致无法展示

解决方法：
给tooltip增加position函数，自动更新位置

tooltip: {
   trigger: 'axis',
   position(
     point: number[],
     _params: unknown,
     _dom: unknown,
     _rect: unknown,
     size: { contentSize: number[] }
   ) {
     const [pointX, pointY] = point;
     const [boxWidth, boxHeight] = size.contentSize;
     const x = boxWidth > pointX ? pointX + 10 : pointX - boxWidth - 10;
     const y = boxHeight > pointY ? 5 : pointY - boxHeight;
     return [x, y];
   },
 },