[apm3] add DInput and XInput support

games/apm3io/kb.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <windows.h>
+
+#include "apm3io/backend.h"
+#include "apm3io/config.h"
+
+HRESULT apm3_kb_init(const struct apm3_kb_config *cfg,
+                     const struct apm3_io_backend **backend);