Fixed image lazy loading.

_includes/lozad.html

@@ -1,7 +1,8 @@
 <!-- image lazy load: https://github.com/ApoorvSaxena/lozad.js -->
 <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/lozad/dist/lozad.min.js"></script>
+
 <script type="text/javascript">
-  const el = document.querySelectorAll('#post-wrapper img');
-  const observer = lozad(el);
+  const imgs = document.querySelectorAll('#post-wrapper img');
+  const observer = lozad(imgs);
   observer.observe();
 </script>

_layouts/post.html

@@ -64,13 +64,19 @@ layout: default
       </div> <!-- .post-meta -->
 
       <div class="post-content">
-
         {% if page.image %}
           <img src="{{ page.image }}">
         {% endif %}
-
-        {{ content }}
-
+        <!-- Add lozad class into image tags. see: <https://github.com/ApoorvSaxena/lozad.js#usage> -->
+        {% if content contains '<img src=' %}
+          {% capture loading %}
+           {{ "/assets/img/commons/loading.png" | relative_url }}
+          {% endcapture %}
+          {% assign replacement = '<img src=' | append: loading | append: ' data-src=' %}
+          {{ content | replace: '<img src=', replacement }}
+        {% else %}
+          {{ content }}
+        {% endif %}
       </div>
 
       <div class="post-tail-wrapper text-muted">