Add libopus to project

Use https://github.com/deltabeard/3ds_portlibs to obtain libopus.

Signed-off-by: Mahyar Koshkouei <deltabeard@users.noreply.github.com>

source/main.c

@@ -10,6 +10,7 @@
 #include <3ds.h>
 #include <dirent.h>
 #include <errno.h>
+#include <opus/opus.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>