Implement About Button Functionality (#3005)

src/citra_qt/aboutdialog.h

@@ -0,0 +1,25 @@
+// Copyright 2017 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#ifndef ABOUTDIALOG_H
+#define ABOUTDIALOG_H
+
+#include <QDialog>
+
+namespace Ui {
+class AboutDialog;
+}
+
+class AboutDialog : public QDialog {
+    Q_OBJECT
+
+public:
+    explicit AboutDialog(QWidget* parent = 0);
+    ~AboutDialog();
+
+private:
+    Ui::AboutDialog* ui;
+};
+
+#endif // ABOUTDIALOG_H