Use .twig instead of .html.twig

source/_layouts/post.html.twig

@@ -1,48 +0,0 @@
- {% extends 'default.html.twig' %}
-
-{% block body_classes 'page--blog page--blog__post' %}
-
-{% block content_wrapper %}
-    <main class="col-md-10">
-        {% include 'post_header' %}
-
-        {% block content %}{% endblock content %}
-
-        {% if page.related -%}
-            <h2>Related Posts</h2>
-
-            <ul>
-                {% for relate in page.related -%}
-                    <li>
-                        <a href="{{ relate.source.url }}">{{ relate.title }}</a>
-                    </li>
-                {% endfor %}
-            </ul>
-        {%- endif %}
-
-        {% if page.tags %}
-            <p class="tags">
-                Tags:
-                {% for tag in page.tags %}
-                    <a href="{{ site.url }}/blog/tags/{{ tag|url_encode(true) }}">{{ tag }}</a>{% if not loop.last %}, {% endif %}
-                {% endfor %}
-            </p>
-        {% endif %}
-
-        <div class="about-author">
-            <h2>About the Author</h2>
-
-            <img src="{{ site.gravatar.url }}?s=50" alt="Picture of Oliver" class="img-circle">
-
-            <p><a href="{{ site.url }}">Oliver Davies</a> is a Drupal Developer and System Administrator based in the UK. He is a Senior Developer at <a href="https://microserve.io">Microserve</a> and also provides freelance consultancy services for Drupal websites and Linux servers.</p>
-        </div>
-
-        {% if page.next_post or page.previous_post %}
-            <ul>
-                {% if page.next_post %}<li>Next post: <a href="{{ page.next_post.url }}">{{ page.next_post.title }}</a></li>{% endif %}
-                {% if page.previous_post %}<li>Previous post: <a href="{{ page.previous_post.url }}">{{ page.previous_post.title }}</a></li>{% endif %}
-            </ul>
-    {% endif %}
-
-    </main>
-{% endblock content_wrapper %}