* Fixed compilation of the ps2avrGB keyboard/firmware
This commit fixes the silent compilation error for the ps2avrGB
keyboard/firmware. This error was caused by a lacking default
keymap which it did not have because all keyboards based on it were
moved to another directory. I also added the required config.h
options so it's possible to compile it again and (probably)
flash it on a b.mini.
Lastly, I updated the README to reflect the current state.
This commit fixes#2425
* Referenced the pearl in the ps2avrGB REAMDE
Added a reference to the pearl keyboard in the README of the ps2avrGB keyboard as it is originally based on the firmware as well.
