Xml Escape for Author Name

The following xml contains a unescaped "&", which is not valid:

    <author>
      <name>Bulma: Free, open source, & modern CSS framework based on Flexbox</name>
      <email>[email protected]</email>
    </author>

This change should fix it.

docs/atom.xml

@@ -9,7 +9,7 @@
     <id>{{ site.url }}</id>
     <updated>{{ site.time | date_to_xmlschema }}</updated>
     <author>
-      <name>{{ site.data.meta.title }}</name>
+      <name>{{ site.data.meta.title | xml_escape }}</name>
       <email>[email protected]</email>
     </author>
     <atom:link href="{{ site.url }}/atom.xml" rel="self" type="application/rss+xml" />