add functionality to display categories, like tags, in blog home page (#1482)

Added the functionality to display categories on the front page of the
blog, just like tags.

_config.yml

@@ -263,6 +263,7 @@ jekyll-archives:
     category: '/blog/category/:name/'
 
 display_tags: ['formatting', 'images', 'links', 'math', 'code'] # these tags will be displayed on the front page of your blog
+display_categories: ['blockquotes'] # these categories will be displayed on the front page of your blog
 
 # -----------------------------------------------------------------------------
 # Jekyll Scholar

_sass/_base.scss

@@ -404,7 +404,7 @@ footer.sticky-bottom {
   }
 }
 
-.tag-list {
+.tag-category-list {
   border-bottom: 1px solid var(--global-divider-color);
   text-align: center;
   padding-top: 1rem;

blog/index.html

@@ -25,8 +25,8 @@ pagination:
   </div>
   {% endif %}
 
-  {% if site.display_tags %}
-  <div class="tag-list">
+  {% if site.display_tags or site.display_categories %}
+  <div class="tag-category-list">
     <ul class="p-0 m-0">
       {% for tag in site.display_tags %}
         <li>
@@ -36,6 +36,17 @@ pagination:
           <p>&bull;</p>
         {% endunless %}
       {% endfor %}
+      {% if site.display_categories.size > 0 and site.display_tags.size > 0 %}
+        <p>&bull;</p>
+      {% endif %}
+      {% for category in site.display_categories %}
+        <li>
+          <i class="fas fa-tag fa-sm"></i> <a href="{{ category | slugify | prepend: '/blog/category/' | relative_url }}">{{ category }}</a>
+        </li>
+        {% unless forloop.last %}
+          <p>&bull;</p>
+        {% endunless %}
+      {% endfor %}
     </ul>
   </div>
   {% endif %}