rgb scheme: blind typing zones

[pshirshov]

This patch includes new RGB scheme which highlights blind typing zones.

Build might look like:

#!/usr/bin/env bash
set -euxo pipefail

cd $BASE/framework-qmk

echo "=== Compiling finger_zones keymap via nix-shell (ARM only) ==="
nix-shell --arg avr false --arg teensy false \
    --run "make framework/ansi:finger_zones"