scrolling text improvement

better readability
- only add "shadow" pixels when overlay text is actually scrolling, or displayed value changes very often

wled00/FX_2Dfcn.cpp

@@ -922,6 +922,7 @@ void Segment::drawCharacter(unsigned char chr, int16_t x, int16_t y, uint8_t w,
   uint32_t bgCol = SEGCOLOR(1);
 
   //if (w<5 || w>6 || h!=8) return;
+  if (drawShadow) w++; // one more column for shadow on right side
   for (int i = 0; i<h; i++) { // character height
     int16_t y0 = y + i;
     if (y0 < 0) continue; // drawing off-screen