Hints for gnome-music in main

Hints

• asv-description-first-para-too-short
  :137 - An easy and pleasant way to play your music.
  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-nonstandard-gnome-extension
  :433 - kudos
  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.