[WIP] Commit before rebase of master the small classes introductions

src/Lib/Utils.hh

 #ifndef VIVY_UTILS_H
 #define VIVY_UTILS_H
 
+#ifndef __cplusplus
+#error "This is a C++ header"
+#endif
+
 #include <QString>
 #include <QFileInfo>
 #include <QStringList>

src/UI/DocumentViews/MpvContainer.hh

+#pragma once
+
+#ifndef __cplusplus
+#error "This is a C++ header"
+#endif
+
+#include "../../Lib/Utils.hh"
+
+struct mpv_handle;
+
+namespace Vivy
+{
+class MpvContainer : public QWidget {
+    VIVY_UNMOVABLE_OBJECT(MpvContainer)
+
+private:
+    quint64 wid{ 0 };
+    mpv_handle *mpv{ nullptr };
+
+public:
+    explicit MpvContainer() noexcept;
+    ~MpvContainer() noexcept override;
+
+signals:
+    void mpvEvent();
+};
+}