Add gamepad support to the desktop build

Co-Authored-By: deepseek-v4.1-flash (opencode-go) via CodeCraft

INSTALL.md

@@ -46,8 +46,9 @@ cargo build --release
 ./target/release/dungeoncraft
 ```
 
-On Linux the build needs the ALSA headers (`alsa-lib` / `libasound2-dev`); the sound goes through ALSA (PipeWire and
-PulseAudio take it). The settings, the autosave, the campaign progress and the profile are kept as files in the
+On Linux the build needs the ALSA headers (`alsa-lib` / `libasound2-dev`) and libudev for gamepads
+(`libudev-dev`); the sound goes through ALSA (PipeWire and PulseAudio take it). Gamepads are read directly on the
+desktop (gilrs, hot-plug included); the browser build uses the browser's Gamepad API. The settings, the autosave, the campaign progress and the profile are kept as files in the
 data folder: `~/.local/share/dungeoncraft/` (Linux, or `$XDG_DATA_HOME/dungeoncraft`), `%APPDATA%\DungeonCraft`
 (Windows), `~/Library/Application Support/DungeonCraft` (macOS); `DUNGEONCRAFT_DATA` chooses another one.
 *Save Game* and saved campaigns land in its `saves/` folder; *Load Game* opens the system file dialog there (on