docs: Add NetPanzer to User.md

docs/markdown/Users.md

@@ -116,6 +116,7 @@ format files
  - [mrsh](https://github.com/emersion/mrsh), a minimal POSIX shell
  - [Nautilus](https://gitlab.gnome.org/GNOME/nautilus), the GNOME file manager
  - [Nemo](https://github.com/linuxmint/nemo), the file manager for the Cinnamon desktop environment
+ - [NetPanzer](https://github.com/netpanzer/netpanzer), a 2D online multiplayer tactical warfare game designed for fast action combat
  - [nvme-cli](https://github.com/linux-nvme/nvme-cli), NVMe management command line interface
  - [OcherBook](https://github.com/ccoffing/OcherBook), an open source book reader for Kobo devices
  - [oomd](https://github.com/facebookincubator/oomd), a userspace Out-Of-Memory (OOM) killer for Linux systems