refactor(frontmatter): edit image frontmatter processing to include post field

Author: Slavetomints

_layouts/post.html

@@ -36,7 +36,7 @@ <h1 data-toc-skip>{{ page.title }}</h1>
         </span>
       {% endif %}
 
-      {% if page.image %}
+      {% if page.image and page.image.post != false %}
         {% capture src %}src="{{ page.image.path | default: page.image }}"{% endcapture %}
         {% capture class %}class="preview-img{% if page.image.no_bg %}{{ ' no-bg' }}{% endif %}"{% endcapture %}
         {% capture alt %}alt="{{ page.image.alt | xml_escape | default: "Preview Image" }}"{% endcapture %}