Hints for font-viewer in main

Hints

• asv-nonstandard-gnome-extension
  <code>org.gnome.FontViewer.appdata.xml:83</code> - <em>kudos</em><br/>This tag is a GNOME-specific extension to AppStream and not part of the official specification. Do not expect it to work in all implementations and in all software centers.
• asv-url-not-secure
  <code>org.gnome.FontViewer.appdata.xml:149</code> - <em>http://fontmanager.github.io/</em><br/>Consider using a secure (HTTPS) URL for this web link.
• asv-developer-info-missing
  <code>org.gnome.FontViewer.appdata.xml</code> - <em></em><br/>This component contains no `developer` element with information about its author.