fix(rss): add proper description value

src/feed.njk

@@ -24,7 +24,7 @@
     <item>
       <title>{{ post.data.title }}</title>
       <link>{{ absolutePostUrl }}</link>
-      <description>{{ post.description }}</description>
+      <description>{{ post.data.description }}</description>
       <pubDate>{{ post.date | dateToRfc822 }}</pubDate>
       <category>{{ post.data.type }}</category>
       <dc:creator>{{ post.data.author or metadata.author }}</dc:creator>