Enhance language dropdown accessibility with lang attributes

Added proper lang attributes to each language option in the doctrine page language selector for improved screen reader support and semantic HTML compliance.

Author: liberaldev

doctrine/index.html

@@ -24,12 +24,12 @@ <h1>The Rails Doctrine.</h1>
         </label>
         <div class="language__options">
           <ul>
-            <li><a href="/doctrine/de"><span>Deutsch</span></a></li>
-            <li><a href="/doctrine/es"><span>Español</span></a></li>
-            <li><a href="/doctrine/fr"><span>Français</span></a></li>
-            <li><a href="/doctrine/ru"><span>Russian</span></a></li>
-            <li><a href="/doctrine/zh_cn"><span>简体中文</span></a></li>
-            <li><a href="/doctrine/zh_tw"><span>繁體中文</span></a></li>
+            <li lang="de"><a href="/doctrine/de"><span>Deutsch</span></a></li>
+            <li lang="es"><a href="/doctrine/es"><span>Español</span></a></li>
+            <li lang="fr"><a href="/doctrine/fr"><span>Français</span></a></li>
+            <li lang="en"><a href="/doctrine/ru"><span>Russian</span></a></li>
+            <li lang="zh-CN"><a href="/doctrine/zh_cn"><span>简体中文</span></a></li>
+            <li lang="zh-TW"><a href="/doctrine/zh_tw"><span>繁體中文</span></a></li>
           </ul>
         </div>
       </div>