Fixed doc [skip ci]

Author: vuongxuongminh

README.md

@@ -2,7 +2,7 @@
     <a href="https://github.com/yiisoft" target="_blank">
         <img src="https://avatars0.githubusercontent.com/u/50674062" height="100px">
     </a>
-    <h1 align="center">Việt Nam Valdation</h1>
+    <h1 align="center">Việt Nam Validation</h1>
     <br>
 </p>