Add option to use connection PIN ("1234")

Author: PowerBroker2

examples/ESP32_Bluetooth_Serial/ESP32_Bluetooth_Serial.ino

@@ -21,6 +21,7 @@ void setup()
 #endif
 
   DEBUG_PORT.begin(115200);
+  //SerialBT.setPin("1234");
   ELM_PORT.begin("ArduHUD", true);
 
   if (!ELM_PORT.connect("OBDII"))