Users.md: add qboot [skip ci]

It's worth to list a meson project building a firmware.

docs/markdown/Users.md

@@ -97,6 +97,7 @@ format files
  - [Pitivi](https://github.com/pitivi/pitivi/), a nonlinear video editor
  - [Playerctl](https://github.com/acrisci/playerctl), mpris command-line controller and library for spotify, vlc, audacious, bmp, cmus, and others
  - [Polari](https://gitlab.gnome.org/GNOME/polari), an IRC client
+ - [qboot](https://github.com/bonzini/qboot), a minimal x86 firmware for booting Linux kernels
  - [radare2](https://github.com/radare/radare2), unix-like reverse engineering framework and commandline tools (not the default)
  - [RxDock](https://gitlab.com/rxdock/rxdock), a protein-ligand docking software designed for high throughput virtual screening (fork of rDock)
  - [SSHFS](https://github.com/libfuse/sshfs), allows you to mount a remote filesystem using SFTP