add last image

content/u/projects/opensource/contents.lr

@@ -2,6 +2,8 @@ title: Open Source
 ---
 subtitle: Open Source literally created ungleich
 ---
+image: /u/image/cards/opensource.jpg
+---
 content:
 
 ## History of Open Source at ungleich

templates/summary-page.html

@@ -16,7 +16,7 @@
         <img class="card-img-top" src="{{ childpage.image }}"
              alt="{{ childpage.title }}">
         {% else %}
-        <img class="card-img-top" src="/u/image/cards/placeholder.png"
+        <img class="card-img-top" src="/u/image/cards/placeholder.jpg"
              alt="{{ childpage.title }}">
         {% endif %}
         </a>