all: move headers to include folder

Signed-off-by: Mahyar Koshkouei <mk@deltabeard.com>

include/opus.h

@@ -0,0 +1,20 @@
+#include <opus/opusfile.h>
+#include "playback.h"
+
+void setOpus(struct decoder_fn* decoder);
+
+int initOpus(const char* file);
+
+uint32_t rateOpus(void);
+
+uint8_t channelOpus(void);
+
+uint64_t decodeOpus(void* buffer);
+
+void exitOpus(void);
+
+int playOpus(const char* in);
+
+uint64_t fillOpusBuffer(int16_t* bufferOut);
+
+int isOpus(const char* in);