SK6812 RGBW LED Support

@wizard

SK6812 RGBW testing update.
The strip is connected to the Ch-0 of IO Expander but I guess, this should not matter.
Strip works and the result is 100% expected but it is also 100% incorrect.
Here my very simple test pattern, only RED LEDs should be On:

export function beforeRender(delta)
{

}

export function render(index)
{

  r = 1
  g = 0
  b = 0
  
  rgb(r, g, b)
}

Instead they are sequentially Red, Green/White and Blue
This is 100% expected behavior. The reason is:
At least current FW version (3.2) of Pixelblase send 24-bit of data but
this LED expects 32-bit. And of course, number of LEDs must be set
to 400 in order to light up all LEDs.
Picture is attached:

In order to overcome this incompatibility some sort of RGB-to-RGBW re-mapping
function should be created (another words, 24-bit to 32-bit mapping is required)
I guess, this could be done because the sequence repeats every 96-bits.
Let me see how this will go.
But I am open to any other reasonable solution if anyone can suggest something.

PS,
Of course, I can switch to ESP8266 with Fast LEDs or WLED SW but I would
like to stay with Pixelblaze.