Mention another alternate driver for RGBPanels with Adafruit::GFX support and up to at least 256x256, includes unsupported panels like AB/AC and FM6126A

https://github.com/adafruit/RGB-matrix-Panel/pull/62 mentions a new driver I just wrote.

http://marc.merlins.org/perso/arduino/post_2020-01-01_Running-FastLED_-Adafruit_GFX_-and-LEDMatrix-code-on-High-Resolution-RGBPanels-with-a-Raspberry-Pi.html explains the new solution in https://github.com/marcmerlin/ArduinoOnPc-FastLED-GFX-LEDMatrix  

This solution allows you to build arduino code so that it works on linux and uses these layers:
- https://github.com/marcmerlin/ArduinoOnPc-FastLED-GFX-LEDMatrix
- https://github.com/marcmerlin/Framebuffer_GFX is the base arduino framebuffer that also supports more 2D arduino code in addition to Adafruit::GFX
- https://github.com/marcmerlin/FastLED_RPIRGBPanel_GFX is the driver that bridges that framebuffer and the APIs it supports (FastLED, Adafruit::GFX, and LEDMatrix), with rpi-rgb-led-matrix for display

Review linked PR #62 and the ArduinoOnPc-FastLED-GFX-LEDMatrix, Framebuffer_GFX, and FastLED_RPIRGBPanel_GFX repositories first. Find where alternate drivers are documented, then add a concise mention of the Linux/Raspberry Pi solution and its Adafruit::GFX and high-resolution panel support. Done when the linked solution and AB/AC and FM6126A support are clearly described.

Written by the indexing model from the issue text.