feat: show author for posts that specify one (#122)

* feat: show author for posts that specify one

Posts by default inherit the site's author, but it's possible to
override that per post, which affects--e.g.--the RSS metadata. For posts
that do so, we don't currently show that anywhere in the theme.

Add a new piece of metadata to posts, along with the date and reading
time, that displays the author only when it's not inherited from the
site.

* Update pagination-item.html

---------

Co-authored-by: JT <jeffreytse.mail@gmail.com>

_includes/views/pagination-item.html

@@ -17,6 +17,9 @@ <h2 class="post-title">
   </h2>
   <div class="post-meta">
     <span class="post-date"><i class="fa fa-calendar"></i> {{ post.date | date: date_format }}</span>
+    {%- if post.author -%}
+    <span class="post-author left-vsplit"><i class="fa fa-pencil"></i> {{ post.author | escape }}</span>
+    {%- endif -%}
     <span class="post-reading-time left-vsplit"><i class="fa fa-clock-o"></i> {{ reading_time }}</span>
   </div>
   <a class="post-excerpt" href="{{ post_url }}">

_includes/views/post-header.html

@@ -8,6 +8,10 @@ <h2 class="post-subtitle">{{ subheading | default: page.subtitle | escape }}</h2
       <i class="fa fa-calendar"></i> {{ page.date | date: date_format }}
     </time>
 
+    {%- if page.author -%}
+    <span class="post-author left-vsplit"><i class="fa fa-pencil"></i> {{ page.author | escape }}</span>
+    {%- endif -%}
+
     {% assign article = page.content %}
     {% assign lang = page.lang %}
     {%- include functions.html func='get_reading_time' -%}