Hints for mailnag in main

Hints

• asv-developer-name-tag-deprecated
  <code>com.github.pulb.mailnag.metainfo.xml:33</code> - <em></em><br/>The toplevel `developer_name` element is deprecated. Please use the `name` element in a `developer` block instead.
• asv-content-rating-missing
  <code>com.github.pulb.mailnag.metainfo.xml</code> - <em></em><br/>This component has no `content_rating` tag to provide age rating information. You can generate the tag data online by answering a few questions at https://hughsie.github.io/oars/
• asv-developer-info-missing
  <code>com.github.pulb.mailnag.metainfo.xml</code> - <em></em><br/>This component contains no `developer` element with information about its author.