docs: update readme

Author: pengzhanbo

README.md

@@ -5,7 +5,11 @@
 <img src="/example/image-placeholder.svg" alt="logo" style="margin:auto">
 </p>
 
-During project development, placeholder images are generated for content areas where no image resources are prepared.
+<p align="center">During project development, placeholder images are generated for content areas where no image resources are prepared.</p>
+
+<p align="center">
+<span>English</span> | <a href="/README.zh-CN.md">简体中文</a>
+</p>
 
 ## Features
 

README.zh-CN.md

@@ -6,6 +6,10 @@
 </p>
 <p align="center">在项目开发过程中，为未准备好图片资源的内容区域，生成占位图片。</p>
 
+<p align="center">
+<a href="/README.md">English</a> | <span>简体中文</span>
+</p>
+
 ## 特性
 
 - 🗺 本地生成图片