Dear xfce developers,

I would like to ask you to add support for the backlight of intel-based chromebooks (or probably any intel n3060 based notebook for that matter).
First off I have to apologize that I am not submitting a patch myself, but I have no idea how your workflow for accepting patches works etc; I would have created a PR on github or bitbucket or gitlab since I know the procedure there.

I had a look at the source code all the needed change is very small:

in `xfpm-backlight-helper.c` a new item must be added to the `backlight_interfaces`, called "intel_backlight". And that should be it.

Here's the tree from the `/sys/class/backlight` interface:

```
	(xenial)root@localhost:~# find /sys/class/backlight/intel_backlight/
	/sys/class/backlight/intel_backlight/
	/sys/class/backlight/intel_backlight/type
	/sys/class/backlight/intel_backlight/brightness
	/sys/class/backlight/intel_backlight/power
	/sys/class/backlight/intel_backlight/power/control
	/sys/class/backlight/intel_backlight/power/async
	/sys/class/backlight/intel_backlight/power/dark_resume_active
	/sys/class/backlight/intel_backlight/power/runtime_enabled
	/sys/class/backlight/intel_backlight/power/runtime_active_kids
	/sys/class/backlight/intel_backlight/power/runtime_active_time
	/sys/class/backlight/intel_backlight/power/autosuspend_delay_ms
	/sys/class/backlight/intel_backlight/power/runtime_status
	/sys/class/backlight/intel_backlight/power/runtime_usage
	/sys/class/backlight/intel_backlight/power/runtime_suspended_time
	/sys/class/backlight/intel_backlight/bl_power
	/sys/class/backlight/intel_backlight/max_brightness
	/sys/class/backlight/intel_backlight/device
	/sys/class/backlight/intel_backlight/subsystem
	/sys/class/backlight/intel_backlight/resume_brightness
	/sys/class/backlight/intel_backlight/uevent
	/sys/class/backlight/intel_backlight/actual_brightness
```

As you can see, the `brightness` and `max_brightness` handles are there and are working as expected, so just adding "intel_backlight" should work nicely.

Anyway, I would be delighted I you were to include this small change in a future release to get out-of-the-box support for the backlight on chromebooks running xfce using crouton.