Hints for cmake-gui in main

Hints

• asv-description-first-para-too-short
  org.cmake.CMake-GUI.metainfo.xml:10 - CMake is a cross-platform, open-source build system generator.
  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.