Hints for luanti in main

Hints

• asv-description-first-para-too-short
  <code>net.minetest.minetest.metainfo.xml:36</code> - <em>Luanti is a block-based sandbox game platform.</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.