Adds new multiplex-mapper for QiangLi Q8 40x20 panel

[JiDudeS]

Panel info page
Got best work results with --led-slowdown-gpio 2

Here some panel identification photos

Pixel arrangement from colorlight calibration tool

mapper work result

[hzeller]

Thanks!
Can you fix the indentation to match the file, i.e. 2 spaces to indent blocks ?

(Also, you have a typo in the word 'column' (should be single L instead of double), might be worthwhile fixing while at it)

[hzeller]

Alright, I fixed the formatting issues and submitted.

[GnuPP]

Hi, thank you for your work.
I'm kind of new into this topic.
I tried to use the Q8 40x20 panel with ./demo -d0 --led-rows=20 --led-cols=40 --led-slowdown-gpio=2
I tested all multiplexing modes but I still do not get any readable output on the panels. Just a few red glimming leds.
Can you provide an example how to use the code on the Q8 40x20 correctly?

Thank you very much!