default image configuration added.

Author: mshindo

_config.yml

@@ -6,7 +6,7 @@ description: Motonori Shindo's Monologue.
 baseurl: "" # the subpath of your site, e.g. /blog
 url: "https://blog.shin.do" # the base hostname & protocol for your site, e.g. http://example.com
 color_scheme: auto # You can choose three modes auto, light, and dark. By default, the auto mode is set, which means the user can choose the light or dark mode themself.
-
+default_image: "/images/lukas-blazek-GnvurwJsKaY-unsplash.jpg"
 
 #-------------------------------
 # Author Settings

_includes/article.html

@@ -19,6 +19,10 @@
       <a class="article__image" href="{{post.url | prepend: site.baseurl}}">
         <img class="lazy" data-src="{{site.baseurl}}{{post.image}}" alt="{{post.title}}">
       </a>
+      {% else %}
+      <a class="article__image" href="{{post.url | prepend: site.baseurl}}">
+        <img class="lazy" data-src="{{site.baseurl}}{{site.default_image}}" alt="{{post.title}}">
+      </a>
       {% endif %}
 
     </div>