feat: i18n support with first translations

src/main/engine/templates/single-post.liquid

@@ -5,7 +5,7 @@
     <main>
       <article class="single-post" data-template="single-post">
         <h1>{{ post.title }}</h1>
-        <div class="post">{{ post.content | markdown: post.id, canonical_post_path_by_slug, canonical_media_path_by_source_path }}</div>
+        <div class="post">{{ post.content | markdown: post.id, canonical_post_path_by_slug, canonical_media_path_by_source_path, language }}</div>
       </article>
     </main>
   </body>