docs: add component registration link (#8378)

src/datetime-picker/README.md

@@ -6,6 +6,8 @@ Used to select time, support date and time dimensions, usually used with the [Po
 
 ### Install
 
+Register component globally via `app.use`, refer to [Component Registration](#/en-US/advanced-usage#zu-jian-zhu-ce) for more registration ways。
+
 ```js
 import { createApp } from 'vue';
 import { DatetimePicker } from 'vant';

src/datetime-picker/README.zh-CN.md

@@ -6,6 +6,8 @@
 
 ### 引入
 
+通过以下方式来全局注册组件，更多注册方式请参考[组件注册](#/zh-CN/advanced-usage#zu-jian-zhu-ce)。
+
 ```js
 import { createApp } from 'vue';
 import { DatetimePicker } from 'vant';