Add audio resource enum

Also default tone_id and nof_repeat to 0 in playAudioResource()

Author: sfe-SparkFro

src/sfe_ublox_cellular_voice.h

@@ -10,6 +10,13 @@ const char* const UBX_CELL_COMMAND_PLAY_AUDIO = "+UPAR";    // Play audio resour
 const char* const UBX_CELL_COMMAND_STOP_AUDIO = "+USAR";    // Stop audio resource
 const char* const UBX_CELL_COMMAND_GENERATE_TONE = "+UTGN"; // Tone generator
 
+typedef enum
+{
+  UBX_CELL_AUDIO_RESOURCE_TONE = 0,
+  UBX_CELL_AUDIO_RESOURCE_MIDI = 1,
+  UBX_CELL_AUDIO_RESOURCE_LOOPBACK = 2
+} UBX_CELL_audio_resource_t;
+
 // Base class for any modules supporting voice calls
 template <typename T>
 class UBX_CELL_VOICE
@@ -60,7 +67,7 @@ class UBX_CELL_VOICE
                                   nullptr, UBX_CELL_STANDARD_RESPONSE_TIMEOUT);
   }
 
-  UBX_CELL_error_t playAudioResource(uint8_t audio_resource, uint8_t tone_id, uint8_t nof_repeat)
+  UBX_CELL_error_t playAudioResource(uint8_t audio_resource, uint8_t tone_id = 0, uint8_t nof_repeat = 0)
   {
     UBX_CELL_error_t err;
     char *command;