Added laptop brightness script

(cherry picked from commit f4f32533c3)

bin/brightness

@@ -0,0 +1,24 @@
+#!/bin/fish
+
+set backlight_device $argv[1]
+set action $argv[2]
+set dvalue $argv[3]
+
+echo Backlight device: $backlight_device Bumping: $action By: $dvalue
+set current_value (cat $backlight_device)
+
+if test $action = up
+	echo (math $current_value + $dvalue) > $backlight_device
+else if test $action = down
+	set newVal (math $current_value - $dvalue)
+	if test $newVal -lt 100
+		set newVal 100 
+	end
+	echo New brightness value: $newVal
+	echo $newVal > $backlight_device
+else
+	exit 2
+end
+
+
+