docs(Modal): add simplified descriptions (#7408)

close #7393

Author: selicens

components/modal/index.en-US.md

@@ -155,3 +155,5 @@ When you need context information (for example, using a globally registered comp
   });
 </script>
 ```
+
+> [App Package Component](/components/app) can be used to simplify the problem of `useModal` and other methods that need to manually implant contextHolder.

components/modal/index.zh-CN.md

@@ -159,3 +159,5 @@ router.beforeEach((to, from, next) => {
   });
 </script>
 ```
+
+> 可通过 [App 包裹组件](/components/app-cn) 简化`useModal`等方法需要手动植入 contextHolder 的问题。