Remove HTML tags from preview

Fixes #24

templates/macros.tera

@@ -1,7 +1,7 @@
 {% macro post_card(article) %}
     <div class="card">
         <h3><a href="{{ article.url }}">{{ article.post.title }}</a></h3>
-        <main><p>{{ article.post.content | escape | truncate(length=200) }}…</p></main>
+        <main><p>{{ article.post.content | striptags | truncate(length=200) }}…</p></main>
         <p>By <a href="/@/{{ article.author.fqn }}/">{{ article.author.display_name }}</a> ⋅ {{ article.date | date(format="%B %e") }}</p>
     </div>
 {% endmacro post_card %}