slapos_rss_style: convert to title, description, author to compatible xml
Ensure to convert the text values to a safer output that will be compatible with XML 1.0. See: https://www.w3.org/TR/REC-xml/#NT-Char
Ensure to convert the text values to a safer output that will be compatible with XML 1.0. See: https://www.w3.org/TR/REC-xml/#NT-Char