chore: update i18n dayjs (element-plus#10603)

Author: iamkun

docs/en-US/guide/i18n.md

@@ -52,6 +52,13 @@ for globally configuring locale and other settings.
 </script>
 ```
 
+## Date and time localization
+
+We use [Day.js](https://day.js.org/docs/en/i18n/i18n) library to manage date and time in components like `DatePicker`. It is important to set a proper locale in Day.js to make the internationalization fully works. You have to import Day.js's locale config separately.
+```
+import 'dayjs/locale/zh-cn'
+```
+
 ## CDN Usage
 
 If you are using Element Plus via CDN, then you need to do this, let's again take