Hints for ffmpegthumbs in main

Hints

• asv-summary-has-dot-suffix
  org.kde.ffmpegthumbs.metainfo.xml:65 - Xerador de miniaturas para vídeos que usa FFmpeg.
  The component summary should not end with a dot (`.`).
• asv-description-first-para-too-short
  org.kde.ffmpegthumbs.metainfo.xml:91 - FFmpeg Thumbnailer is a video thumbnail generator for KDE file managers.
  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.