Add a new example to show how to view and edit xlsx file with GUI

examples/xlsx/xlsxwidget/main.cpp

@@ -0,0 +1,35 @@
+#include <QtWidgets>
+#include "xlsxdocument.h"
+#include "xlsxsheetmodel.h"
+
+using namespace QXlsx;
+
+int main(int argc, char **argv)
+{
+    QApplication app(argc, argv);
+
+    //![0]
+    QString filePath = QFileDialog::getOpenFileName(0, "Open xlsx file", QString(), ".xlsx");
+    if (filePath.isEmpty())
+        return -1;
+    //![0]
+
+    //![1]
+    QTabWidget tabWidget;
+    tabWidget.setWindowTitle(filePath + " - Qt Xlsx Demo");
+    tabWidget.setTabPosition(QTabWidget::South);
+    //![1]
+
+    //![2]
+    Document xlsx(filePath);
+    foreach (QString sheetName, xlsx.worksheetNames()) {
+        QTableView *view = new QTableView(&tabWidget);
+        SheetModel *model = new SheetModel(xlsx.worksheet(sheetName), view);
+        view->setModel(model);
+        tabWidget.addTab(view, sheetName);
+    }
+    //![2]
+
+    tabWidget.show();
+    return app.exec();
+}