Add XIAO RP2040 support

src/helpers/rp2040/XiaoRP2040Board.cpp

@@ -0,0 +1,30 @@
+#include "XiaoRP2040Board.h"
+
+#include <Arduino.h>
+#include <Wire.h>
+
+void XiaoRP2040Board::begin() {
+  // for future use, sub-classes SHOULD call this from their begin()
+  startup_reason = BD_STARTUP_NORMAL;
+
+#ifdef P_LORA_TX_LED
+  pinMode(P_LORA_TX_LED, OUTPUT);
+#endif
+
+#ifdef PIN_VBAT_READ
+  pinMode(PIN_VBAT_READ, INPUT);
+#endif
+
+#if defined(PIN_BOARD_SDA) && defined(PIN_BOARD_SCL)
+  Wire.setSDA(PIN_BOARD_SDA);
+  Wire.setSCL(PIN_BOARD_SCL);
+#endif
+
+  Wire.begin();
+
+  delay(10); // give sx1262 some time to power up
+}
+
+bool XiaoRP2040Board::startOTAUpdate(const char *id, char reply[]) {
+  return false;
+}