Hints for kdiff3 in main

Hints

• asv-description-first-para-too-short
  <code>org.kde.kdiff3.appdata.xml:86</code> - <em>KDiff3 is a file and folder diff and merge tool which</em><br/>The first `description/p` paragraph of this component might be too short (&lt; 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.