Adds posts categories to RSS feeds and Blog categories to the Atom one

atom.xml

@@ -13,6 +13,12 @@ regenerate: true
         <uri>{{ site.author.url | xml_escape }}</uri>
     </author>
     <link rel="self" href="{{ site.url }}/atom.xml" type="application/atom+xml"/>
+    {%- for category in site.categories %}
+        <category
+            term="{{ category[0] | downcase | xml_escape }}"
+            scheme="/blog/{{ category[0] | downcase | xml_escape }}"
+            label="{{ category[0] | xml_escape }}"/>
+    {% endfor %}
     <generator uri="https://jekyllrb.com/" version="{{ jekyll.version }}">Jekyll</generator>
     <rights>All rights reserved {{ site.author.name }} {{ site.posts.last.date | date: "%Y" }} - {{ "now" | date: "%Y" }}</rights>
     <subtitle>{{ site.description | xml_escape }}</subtitle>
@@ -25,6 +31,7 @@ regenerate: true
                 <updated>{{ post.last_modified_at | default: post.date | date_to_xmlschema }}</updated>
                 <link rel="alternate" type="text/html" href="{{ site.url }}{{ post.url }}"/>
                 <summary>{{ post.description | xml_escape }}</summary>
+                <category term="{{ post.category | downcase | xml_escape }}"/>
                 <published>{{ post.date | date_to_xmlschema }}</published>
             </entry>
         {%- endunless %}

feed.json

@@ -26,7 +26,8 @@ regenerate: true
                 "name": {{ site.author.name | jsonify }}
             },
             "content_html": "",
-            "summary": {{ post.description | jsonify }}
+            "summary": {{ post.description | jsonify }},
+            "tags": [{{ post.category | jsonify }}]
         }{% unless forloop.last %},{% endunless %}{% endunless %}{% endfor %}
     ]
 }