docs/Users: add Vala Language Server

See https://github.com/benwaffle/vala-language-server

docs/markdown/Users.md

@@ -124,6 +124,7 @@ format files
  - [Terminology](https://github.com/billiob/terminology), a terminal emulator based on the Enlightenment Foundation Libraries
  - [Tilix](https://github.com/gnunn1/tilix), a tiling terminal emulator for Linux using GTK+ 3
  - [Tizonia](https://github.com/tizonia/tizonia-openmax-il), a command-line cloud music player for Linux with support for Spotify, Google Play Music, YouTube, SoundCloud, TuneIn, Plex servers and Chromecast devices
+ - [Vala Language Server](https://github.com/benwaffle/vala-language-server), code intelligence engine for the Vala and Genie programming languages
  - [Valum](https://github.com/valum-framework/valum), a micro web framework written in Vala
  - [Venom](https://github.com/naxuroqa/Venom), a modern Tox client for the GNU/Linux desktop
  - [VMAF](https://github.com/Netflix/vmaf) (by Netflix), a perceptual video quality assessment based on multi-method fusion