Hints for ristretto in main

Hints

• asv-description-first-para-too-short
  org.xfce.ristretto.appdata.xml:77 - Ristretto is an image viewer for the Xfce desktop environment.
  The first `description/p` paragraph of this component might be too short (< 80 characters). Please consider starting with a longer paragraph to improve how the description looks like in software centers and to provide more detailed information on this component immediately in the first paragraph.
• asv-developer-name-tag-deprecated
  org.xfce.ristretto.appdata.xml:191 -
  The toplevel `developer_name` element is deprecated. Please use the `name` element in a `developer` block instead.
• asv-developer-info-missing
  org.xfce.ristretto.appdata.xml -
  This component contains no `developer` element with information about its author.