Docs(i18n): add on-demand

examples/docs/en-US/i18n.md

@@ -108,6 +108,39 @@ Vue.use(Element, {
 new Vue({ i18n }).$mount('#app')
 ```
 
+## Custom i18n in on-demand components
+
+```js
+import Vue from 'vue'
+import DatePicker from 'element/lib/date-picker'
+import VueI18n from 'vue-i18n'
+
+import enLocale from 'element-ui/lib/locale/lang/en'
+import zhLocale from 'element-ui/lib/locale/lang/zh-CN'
+import ElementLocale from 'element-ui/lib/locale'
+
+Vue.use(VueI18n)
+Vue.use(DatePicker)
+
+const messages = {
+  en: {
+    message: 'hello',
+    ...enLocale
+  },
+  zh: {
+    message: '你好',
+    ...zhLocale
+  }
+}
+// Create VueI18n instance with options
+const i18n = new VueI18n({
+  locale: 'en', // set locale
+  messages, // set locale messages
+})
+
+ElementLocale.i18n(key => i18n.t(key))
+```
+
 ## Import via CDN
 
 ```html

examples/docs/zh-CN/i18n.md

@@ -120,6 +120,39 @@ Vue.use(Element, {
 new Vue({ i18n }).$mount('#app')
 ```
 
+## 按需加载里定制 i18n
+
+```js
+import Vue from 'vue'
+import DatePicker from 'element/lib/date-picker'
+import VueI18n from 'vue-i18n'
+
+import enLocale from 'element-ui/lib/locale/lang/en'
+import zhLocale from 'element-ui/lib/locale/lang/zh-CN'
+import ElementLocale from 'element-ui/lib/locale'
+
+Vue.use(VueI18n)
+Vue.use(DatePicker)
+
+const messages = {
+  en: {
+    message: 'hello',
+    ...enLocale
+  },
+  zh: {
+    message: '你好',
+    ...zhLocale
+  }
+}
+// Create VueI18n instance with options
+const i18n = new VueI18n({
+  locale: 'en', // set locale
+  messages, // set locale messages
+})
+
+ElementLocale.i18n(key => i18n.t(key))
+```
+
 ## 通过 CDN 的方式加载语言文件
 
 ```html