add PIN_BUZZER to variants with built-in speaker

Author: hathach

variants/circuitplayground_nrf52840/variant.h

@@ -54,14 +54,17 @@ extern "C"
 #define LED_STATE_ON         1         // State when LED is litted
 
 // Buttons
-#define PIN_BUTTON1          (4)
-#define PIN_BUTTON2          (5)
+#define PIN_BUTTON1          (4)    // Button A (Left)
+#define PIN_BUTTON2          (5)    // Button B (Right)
 
 // Microphone
 #define PIN_PDM_DIN           24
 #define PIN_PDM_CLK           25
 #define PIN_PDM_PWR           -1  // not used
 
+// Buzzer
+#define PIN_BUZZER            12
+
 /*
  * Analog pins
  */

variants/clue_nrf52840/variant.h

@@ -52,14 +52,17 @@ extern "C"
 #define LED_STATE_ON         1         // State when LED is litted
 
 // Buttons
-#define PIN_BUTTON1             (5)
-#define PIN_BUTTON2             (11)
+#define PIN_BUTTON1          (5)    // Button A
+#define PIN_BUTTON2          (11)   // Button B
 
 // Microphone
 #define PIN_PDM_DIN           35
 #define PIN_PDM_CLK           36
 #define PIN_PDM_PWR           -1  // not used
 
+// Buzzer
+#define PIN_BUZZER            46
+
 /*
  * Analog pins
  */