Colorduino plasma demo, matrix test and browser simulator

- ColorduinoPlasma sketch and Colorduino library v1.2.6 (lincomatic @ fff7bd3)
- ColorduinoMatrixTest hardware test sketch
- web/index.html: bit-accurate port of the plasma with large resolutions
- prebuilt 16 MHz firmware (with and without Optiboot)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libraries/Colorduino/library.properties

@@ -0,0 +1,10 @@
+name=Colorduino
+version=1.2.6
+author=Sam C. Lin <lincomatic@hotmail.com>
+maintainer=Sam C. Lin <lincomatic@hotmail.com>
+sentence=Arduino Interface Library for ITeadStudio Colorduino and Colors Shield
+paragraph=Arduino Interface Library for ITeadStudio Colorduino and Colors Shield
+category=Display
+url=https://github.com/lincomatic/Colorduino
+architectures=avr
+includes=Colorduino.h