Please Mention SmartMatrix::GFX as a compat layer for LEDMatrix on top of RGB Panels

[marcmerlin]

As per #10 , people who wrote code using your library API can now port that code on top of RGB Panels without any code changes.

FastLED/LEDMatrix compat library: https://github.com/marcmerlin/SmartMatrix_GFX
SmartMatrix: https://github.com/pixelmatix/SmartMatrix
Example code that becomes compatible with RGB Panels, whether it was written for Adafruit::GFX, FastLED, or LEDMatrix: https://github.com/marcmerlin/FastLED_NeoMatrix_SmartMatrix_LEDMatrix_GFX_Demos/

thanks.