📌 Default NeoPixel pin for MKS Robin E3/E3D (#23060)

Marlin/src/pins/stm32f1/pins_MKS_ROBIN_E3_common.h

@@ -64,6 +64,11 @@
   #define Z_MIN_PROBE_PIN                   PB1
 #endif
 
+// LED driving pin
+#ifndef NEOPIXEL_PIN
+  #define NEOPIXEL_PIN                      PA2
+#endif
+
 //
 // Steppers
 //