shared_widget: Add SPDX header

src/yuzu/configuration/shared_widget.cpp

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
 #include <functional>
 #include <limits>
 #include <typeinfo>

src/yuzu/configuration/shared_widget.h

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
 #pragma once
 
 #include "yuzu/configuration/configuration_shared.h"