Hints for nicotine in main

Hints

• asv-description-first-para-too-short
  org.nicotine_plus.Nicotine.appdata.xml:22 - Nicotine+ is a graphical client for the Soulseek peer-to-peer network.
  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
  org.nicotine_plus.Nicotine.appdata.xml:246 - 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.
• asv-developer-name-tag-deprecated
  org.nicotine_plus.Nicotine.appdata.xml:255 -
  The toplevel `developer_name` element is deprecated. Please use the `name` element in a `developer` block instead.