Add backlight dimming after timeout

[DJFliX]

I implemented backlight dimming and added a few "registers" for configuring it (REG_ID_BK3 and REG_ID_BK4). I wasn't sure how much of the logic you wanted to expose in registers, so I decided to add some variables in backlight.h instead of bringing everything to the registers.

I'm running the changes on my board and it seems to be working as intended: disabling the timeout disables dimming. And changing the timeout does result in a dimmer backlight. I'm pretty sure the alarm/timing could be improved but I didn't want to fire too many events and risk getting in the way of other tasks.

[arturo182]

Thank you for the submission, I'm a bit low on time right now so it might take a bit before I can have a proper look at this, but please know that it is appreciated :)

[DJFliX]

No worries! I noticed that the workflow failed because of multiple definition of last_triggered';` (as well as all the other variables I added). Somehow this didn't happen for me locally and I'm not entirely sure what causes it. I'll enable workflows on a different branch to see if I can identify and fix the issue there before I turn this branch into a mess.

Edit: ok, apparently I was using an outdated docker image (which had an older version of some key components in the compilation process). I've forked the docker image that I used and updated it. After that I was able to reproduce the issue I saw in the workflow on my machine. Then I decided to mimic the approach that I saw somewhere else in this project and introducing a struct named self inside of backlight.c (as opposed to defining the variables in backlight.h). I did take a course in c a long time ago and I thought declaring variables in header files was the norm back then. But maybe I'm mistaken 🤷. Anyhow, this seems to work 🤡