fix: add variable for support internal built in switch (espressif#9499)

fix: add variable for support internal built in switch

Co-authored-by: Me No Dev <me-no-dev@users.noreply.github.com>

Author: SooDragon

variants/Geekble_ESP32C3/pins_arduino.h

@@ -7,6 +7,10 @@ static const uint8_t LED_BUILTIN = 10;
 #define BUILTIN_LED LED_BUILTIN  // backward compatibility
 #define LED_BUILTIN LED_BUILTIN  // allow testing #ifdef LED_BUILTIN
 
+static const uint8_t SW_BUILTIN = 9;
+#define BUILTIN_SW SW_BUILTIN  // backward compatibility
+#define SW_BUILTIN SW_BUILTIN  // allow testing #ifdef SW_BUILTIN
+
 static const uint8_t TX = 21;
 static const uint8_t RX = 20;