Merge pull request #289 from adam2872/RAK4631-user-button

Implement user button on RAK4631 using analogue pin 31 (same as MT)

src/helpers/nrf52/RAK4631Board.cpp

@@ -26,6 +26,10 @@ void RAK4631Board::begin() {
   pinMode(PIN_USER_BTN, INPUT_PULLUP);
 #endif
 
+#ifdef PIN_USER_BTN_ANA
+  pinMode(PIN_USER_BTN_ANA, INPUT_PULLUP);
+#endif
+
 #if defined(PIN_BOARD_SDA) && defined(PIN_BOARD_SCL)
   Wire.setPins(PIN_BOARD_SDA, PIN_BOARD_SCL);
 #endif