* Fix backlight initial value matching the actual brightness level
The initial value is `0`. If the actual brightness is also `0` you see
`%percentage%` token as text, it’s not being replaced. Since
`m_brightness` is an `int` the initial value could be just `-1` since
the actual brightness is never goes below zero. Thus this bug will never
show up again because actual brightness on first render won’t match
the “old” `m_brightness` value.
See also for more detailed explanation of the bug:
https://github.com/polybar/polybar/discussions/3079#discussioncomment-8169932
* Add docs
---------
Co-authored-by: Viacheslav Lotsmanov <lotsmanov89@gmail.com>
8e04f15ed6