docs($plugin-last-updated): update

Author: ulivz

packages/docs/docs/plugin/official/plugin-last-updated.md

@@ -23,20 +23,31 @@ module.exports = {
 
 ### transformer
 
-- Type: `function`
+- Type: `(timestamp: number, lang: string) => string`
 - Default: `undefined`
 
 By default, this plugin produces a 13-bit timestamp for each page, you can also pass in a transformer to convert it to any format that you want.
 
 ``` javascript
-const timeago = require("timeago.js");
+const moment = require('moment');
 
 module.exports = {
   plugins: [
     [ 
       'last-updated',
-      { transformer: timeago.format }
+      { 
+        transformer: (timestamp, lang) => {
+          moment.locale(lang)
+          return moment(timestamp).fromNow()
+        }
+      }
     ]
   ]
 }
 ```
+
+::: tip
+If you are running in [i18n](../../guide/i18n.md) mode, you can also use the second argument `lang` to generate time strings for different languages.
+
+Note that in VuePres, we follow this spec: [W3C > Language tags in HTML and XML](https://en.wikipedia.org/wiki/Language_localisation), so `en-US` uses hyphens (`-`) instead of underscores (`_`). Please make sure that the library you are using follows this spec, otherwise please convert it yourself.
+:::

packages/docs/docs/zh/plugin/official/plugin-last-updated.md

@@ -23,20 +23,31 @@ module.exports = {
 
 ### transformer
 
-- 类型: `function`
+- Type: `(timestamp: number, lang: string) => string`
 - 默认值: `undefined`
 
 默认情况下，本插件为每个页面生成一个 13 位的时间戳，你可以传入一个 transformer 将其转换为你想要的任何格式。
 
 ``` javascript
-const timeago = require("timeago.js");
+const moment = require('moment');
 
 module.exports = {
   plugins: [
     [ 
       'last-updated',
-      { transformer: timeago.format }
+      { 
+        transformer: (timestamp, lang) => {
+          moment.locale(lang)
+          return moment(timestamp).fromNow()
+        }
+      }
     ]
   ]
 }
 ```
+
+::: tip
+如果你在 [i18n](../../guide/i18n.md) 模式下运行，你还可以使用第二个参数 `lang` 为不同语言生成时间字符串。
+
+请注意，在VuePres中，我们遵循以下规范：[W3C > Language tags in HTML and XML](https://en.wikipedia.org/wiki/Language_localisation)，因此 `zh-CN` 使用连字符（`-`）而不是下划线（`_`）。 请确保你使用的库遵循此规范，否则请自行转换。
+:::