led-backlight-osx

For certain keyboards, [`led-backlight-osx`](https://github.com/pykler/led-backlight-osx) needs to be installed.

```shell
mkdir -p ~/bin
wget https://raw.githubusercontent.com/pykler/led-backlight-osx/master/led-backlight-osx
chmod +x led-backlight-osx
mv led-backlight-osx ~/bin
```