Moved include files to a proper sdl3game include directory

src/json_helpers.c

@@ -2,11 +2,11 @@
 #include <string.h>
 #include <sdlerror.h>
 
-#include "json_helpers.h"
-#include "game.h"
-#include "heap.h"
-#include "staticstring.h"
-#include "registry.h"
+#include <sdl3game/json_helpers.h>
+#include <sdl3game/game.h>
+#include <sdl3game/heap.h>
+#include <sdl3game/staticstring.h>
+#include <sdl3game/registry.h>
 
 ErrorContext *get_json_object_value(json_t *obj, char *key, json_t **dest)
 {