chuni/chusan: added LED output to DLLs (will break most DLLs)

Credits: somewhatlurker, skogaby
https://dev.s-ul.net/skogaby/segatools/-/blob/ongeki-15093/

chuniio/serialimpl.h

@@ -0,0 +1,15 @@
+/*
+    Serial LED implementation for chuniio
+    
+    Credits:
+    somewhatlurker, skogaby
+*/
+
+#pragma once
+
+#include <windows.h>
+
+#include "chuniio/leddata.h"
+
+HRESULT led_serial_init(wchar_t led_com[12], DWORD baud);
+void led_serial_update(struct _chuni_led_data_buf_t* data);