For string type cell, Cell::value() return the string instead of the index

src/xlsx/xlsxworksheet_p.h

@@ -35,6 +35,7 @@ namespace QXlsx {
 
 class XmlStreamWriter;
 class XmlStreamReader;
+class SharedStrings;
 
 struct XlsxUrlData
 {
@@ -179,6 +180,8 @@ public:
     void readColumnsInfo(XmlStreamReader &reader);
     void readMergeCells(XmlStreamReader &reader);
 
+    SharedStrings *sharedStrings() const;
+
     Workbook *workbook;
     Drawing *drawing;
     QMap<int, QMap<int, QSharedPointer<Cell> > > cellTable;