add mandatory build flags for -S2 and -C3 (virtual USB)

I was wondering why sometimes the new MCUs still work better in Arduino IDE, so compared our build flags to what is used in Arduino IDE:

-S2 always has -DARDUINO_USB_MODE=0
-C3 always has -DARDUINO_USB_MODE=1
-S3 supports all possible modes

wled00/wled.cpp

@@ -268,7 +268,10 @@ void WLED::setup()
   #endif
 
   Serial.begin(115200);
-  Serial.setTimeout(50);
+  #if !ARDUINO_USB_CDC_ON_BOOT
+  Serial.setTimeout(50);  // this causes troubles on new MCUs that have a "virtual" USB Serial (HWCDC)
+  #else
+  #endif
   #if defined(WLED_DEBUG) && defined(ARDUINO_ARCH_ESP32) && (defined(CONFIG_IDF_TARGET_ESP32S2) || defined(CONFIG_IDF_TARGET_ESP32C3) || ARDUINO_USB_CDC_ON_BOOT)
   delay(2500);  // allow CDC USB serial to initialise
   #endif