Add the installer, uninstaller, and generated docs

default/systemd/system-sleep/keyboard-backlight

@@ -0,0 +1,20 @@
+#!/bin/bash
+
+# Turn off keyboard backlight before hibernate to prevent hang on power-off.
+# The ASUS keyboard controller can block S4 shutdown if LEDs are active.
+
+sleep_action=${SYSTEMD_SLEEP_ACTION:-$2}
+
+if [[ $1 == "pre" && $sleep_action == "hibernate" ]]; then
+  device=""
+  for candidate in /sys/class/leds/*kbd_backlight*; do
+    if [[ -e "$candidate" ]]; then
+      device="$(basename "$candidate")"
+      break
+    fi
+  done
+
+  if [[ -n "$device" ]]; then
+    brightnessctl -d "$device" set 0 >/dev/null 2>&1
+  fi
+fi