Update backlight status more immediately-ish

with a USR1 to i3status

i3/config

@@ -106,8 +106,8 @@ bindsym XF86AudioLowerVolume exec pactl set-sink-volume 0 -1000
 bindsym XF86AudioRaiseVolume exec pactl set-sink-volume 0 +1000
 bindsym XF86AudioMute exec pactl set-sink-mute 0 toggle
 
-bindsym XF86MonBrightnessDown exec xbacklight -5
-bindsym XF86MonBrightnessUp exec xbacklight +5
+bindsym XF86MonBrightnessDown exec ~/.i3status-update-do xbacklight -5
+bindsym XF86MonBrightnessUp exec ~/.i3status-update-do xbacklight +5
 
 bindsym XF86Calculator exec i3lock -c ed1c24
 bindsym XF86Tools exec xfce4-screenshooter

i3status-update-do

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+"$@"
+exec kill -USR1 $(pidof i3status)