fix low volume due to wrong init of audioDAC_data

add support for mixing stereo to mono through dsp_processor (fixes #106)
add sdkconfigs to github action workflow
suppress warnings from flac git submodule
remove unused variable and address some compiler warnings
remove some dead code

Signed-off-by: Karl Osterseher <karl_osterseher@gmx.at>

components/network_interface/wifi_interface.c

@@ -4,9 +4,10 @@
 
     Must be taken over/merge with wifi provision
 */
-
 #include "wifi_interface.h"
 
+#include <string.h>  // for memcpy
+
 #include "esp_event.h"
 #include "esp_log.h"
 #include "esp_mac.h"
@@ -20,8 +21,6 @@
 #include "nvs_flash.h"
 
 #if ENABLE_WIFI_PROVISIONING
-#include <string.h>  // for memcpy
-
 #include "wifi_provisioning.h"
 #endif