Added improved logic for sleep.

- adds a notification before sleep
- fixes storing and reverting the brightness changing
- sets brightness half of current rather than a discrete number.

sway/config.d/autostart

@@ -14,8 +14,9 @@ exec --no-startup-id autotiling
 
 ### Idle configuration
 exec swayidle -w \
-         timeout 285 'light -I && light -S 5' \
-              resume 'light -O' \
+         timeout 280 notify-send "鈴 sleeping in 20 seconds" -t 5000 -c 'sleep' \
+         timeout 285 'light -O && let "a = $(light -G) / 2" && light -S $a '\
+              resume 'light -I' \
          timeout 300 'swaylock-fancy' \
          timeout 600 'swaymsg "output * dpms off"' \
               resume 'swaymsg "output * dpms on"' \