Add support for 2-pin 2 color leds!

[Rimbaldo]

Hi! Would it be possible to add support for 2 pin 2 color leds? When one pin is cathode, one color is lit, when it’s anode, another color is lit, and when rapid switching between the two pins a third color is lit.

There are some old libraries that implemented this, but they are not complete as yours!!

Like these ones below:

https://github.com/JamesCoyle/BiLED

https://github.com/wolfgang42/bicolorled/blob/master/examples/MultiSpeed/MultiSpeed.ino

Thanks!