backlight device not found

The backlight slider does not show up and i'm getting an error message that swaync is not able find the device:
```
** (swaync:226274): WARNING **: 13:31:21.692: backlightUtil.vala:41: Could not find device /sys/class/backlight/amdgpu_b11/brightness
```
But the device does exist:
``` bash
Me@MyDevice [01:30:00 PM] [/sys/class/backlight/amdgpu_bl1]
-> % l
Permissions Size User Date Modified Name
.r--r--r-- 4.1k root 30 Sep 13:27 actual_brightness
.rw-r--r-- 4.1k root 30 Sep 13:27 bl_power
.rw-r--r-- 4.1k root 30 Sep 13:27 brightness
lrwxrwxrwx - root 30 Sep 13:27 device -> ../../card1-eDP-1
.r--r--r-- 4.1k root 30 Sep 13:27 max_brightness
drwxr-xr-x - root 30 Sep 13:27 power
.r--r--r-- 4.1k root 30 Sep 13:27 scale
lrwxrwxrwx - root 30 Sep 13:27 subsystem -> ../../../../../../../../class/backlight
.r--r--r-- 4.1k root 30 Sep 13:27 type
.rw-r--r-- 4.1k root 30 Sep 13:27 uevent
```

**To Reproduce**
Add the backlight widget to the config and configure it:
```
"widgets": [
"backlight",
"volume",
"mpris",
"title",
"dnd",
"notifications",
"buttons-grid"
],
"widget-config":{
"backlight": {
"subsystem": "backlight",
"device": "amdgpu_b11"
},
```

**Expected behavior**
Get a slider to control the backlight

**Desktop (please complete the following information):**
- OS: Arch
- Installed swaync as official package

Start at backlightUtil.vala:41 and compare the configured device name, amdgpu_b11, with the available /sys/class/backlight/amdgpu_bl1 path. Reproduce with the backlight widget configuration from the issue and verify that the widget finds the device and displays a working brightness slider.

Written by the indexing model from the issue text.