Effect matrix now uses subpixel rendering for smoother movements.

include/effect_matrix.h

@@ -9,7 +9,7 @@
 class MatrixEffectColumn {
 protected:
     Window* window;
-    uint8_t x, y;
+    accum88 x, y;
     uint8_t length = 1;
     uint8_t _direction = 2;
     bool _random_direction = false;