fix toggle theme button

Author: capital-G

_includes/default/navbar.html

@@ -35,8 +35,16 @@
         </a>
       </li>
       {% endfor %}
-      <li>
-        <a id="theme-toggle" aria-label="Theme Toggle" onclick="themeToggle()" title="Toggle between Light and Dark theme"></a>
+      <li class="icon">
+        <a
+          class="icon"
+          id="theme-toggle"
+          aria-label="Theme Toggle"
+          onclick="themeToggle()"
+          title="Toggle between Light and Dark theme"
+        >
+          <i class="fa-solid fa-circle-half-stroke"></i>
+        </a>
       </li>
     </ul>