Update Charts/MiniArea props type

实测, 字符串应该没有问题. https://github.com/alibaba/BizCharts/blob/74e8bcfd18aa936abdbb6af9fc591f45b3a1f2c2/doc/tutorial/data.md

src/components/Charts/MiniArea/index.d.ts

@@ -21,7 +21,7 @@ export interface IMiniAreaProps {
   xAxis?: IAxis;
   yAxis?: IAxis;
   data: Array<{
-    x: number;
+    x: number | string;
     y: number;
   }>;
 }