fix(post): apply lang attr to the article content

Author: at-wr

src/pages/blog/[...slug].astro

@@ -75,7 +75,7 @@ const { Content } = await post.render();
                 <span class="inline-block w-0 h-px overflow-hidden">c13n</span>
             </div>
         </div>
-        <article class="animate">
+        <article class="animate" lang="zh">
             <Content />
         </article>
     </Container>