!20549 calc计算特性添加使用方法

Merge pull request !20549 from limeng/calc_add_sample

zh-cn/application-dev/reference/arkui-ts/ts-universal-attributes-size.md

@@ -76,6 +76,11 @@ struct SizeExample {
         Text('no layoutWeight')
           .size({ width: '30%', height: 110 }).backgroundColor(0xD2B48C).textAlign(TextAlign.Center)
       }.size({ width: '90%', height: 140 }).backgroundColor(0xAFEEEE)
+      // calc计算特性
+      Text('calc:').fontSize(12).fontColor(0xCCCCCC).width('90%')
+      Text('calc test').fontSize(50).fontWeight(FontWeight.Bold).backgroundColor(0xFFFAF0).textAlign(TextAlign.Center)
+        .margin('calc(25vp*2)')
+        .size({width:'calc(90%)', height:'calc(50vp + 10%)'})
     }.width('100%').margin({ top: 5 })
   }
 }