Added tone function

Added tone function.
Syntax:
radio.tone(x, y, z);

x = length in mS
y = Amplitude in dB, -30 to 0
z = Frequency in Hertz. (10 to 20000)

Note. After this command the audio is set to Unmute.

TEF6686_ESP32.ino

@@ -534,6 +534,7 @@ void setup() {
   ShowBW();
   setupmode = false;
   sprite.createSprite(313, 18);
+  radio.tone(50, -5, 2000);
 }
 
 void loop() {