update i18n doc

examples/docs/en-US/i18n.md

@@ -202,6 +202,8 @@ Currently Element ships with the following languages:
   <li>Turkmen (tk)</li>
   <li>Tamil (ta)</li>
   <li>Latvian (lv)</li>
+  <li>Afrikaans (af-ZA)</li>
+  <li>Estonian (ee)</li>
 </ul>
 
 If your target language is not included, you are more than welcome to contribute: just add another language config [here](https://github.com/ElemeFE/element/tree/master/src/locale/lang) and create a pull request.

examples/docs/zh-CN/i18n.md

@@ -214,6 +214,8 @@ ElementLocale.i18n(key => i18n.t(key))
   <li>土库曼语（tk）</li>
   <li>泰米尔语（ta）</li>
   <li>拉脱维亚语（lv）</li>
+  <li>南非荷兰语（af-ZA）</li>
+  <li>爱沙尼亚语（ee）</li>
 </ul>
 
 如果你需要使用其他的语言，欢迎贡献 PR：只需在 [这里](https://github.com/ElemeFE/element/tree/master/src/locale/lang) 添加一个语言配置文件即可。