Add aria-current if on the current page

src/_includes/main/navbar.njk

@@ -1,7 +1,13 @@
+{% set currentUrl %}{{ page.url }}{% endset %}
+
 <nav class="navbar">
     <ul class="nav__menu">
         {% for page in collections.pages %}
-            <li><a href="{{ page.url }}">{{ page.data.title or page.data.metadata.title }}</a></li>
+            <li>
+                <a href="{{ page.url }}" {% if currentUrl === page.url %}aria-current="page"{% endif %}>
+                    {{ page.data.title or page.data.metadata.title }}
+                </a>
+            </li>
         {%- endfor %}
         <li><a href="https://leilukin.123guestbook.com/">Guestbook</a></li>
     </ul>