Add owner email to feed

It is required by some podcast directories.

config.toml

@@ -29,6 +29,7 @@ subtitle = "(Nicht nur) Schulische Themen"
 acronym = "SCH"
 
 [extra.itunes]
+owner_email = "schabernack@sbruder.de"
 
 [extra.theme]
 main = "#00a0bd"

templates/rss.xml

@@ -20,6 +20,9 @@
       <link>{{ config.base_url | escape_xml | safe }}</link>
     </image>
     <itunes:author>{{ config.extra.author }}</itunes:author>
+    <itunes:owner>
+      <itunes:email>{{ config.extra.itunes.owner_email }}</itunes:email>
+    </itunes:owner>
     <itunes:summary>{{ config.description }}</itunes:summary>
     <itunes:image href="{{ get_url(path="assets/poster.jpg") | safe }}"/>
     <itunes:subtitle>{{ config.extra.subtitle }}</itunes:subtitle>