Add a new example

examples/xlsx/extractdata/doc/src/extractdata.qdoc

@@ -0,0 +1,16 @@
+/*!
+    \example extractdata
+    \title Extract Data Example
+    \brief This is a simplest Qt Xlsx example.
+    \ingroup qtxlsx-examples
+
+    This example demonstrates how to extract data form existing
+     .xlsx file with Qt Xlsx Library. So lets see how this is achieved.
+
+    This creates a new instance of the all important Document
+    class which gives you access to the Excel workbook and worksheets.
+    \snippet hello/main.cpp 0
+
+    Extracts data from current worksheet.
+    \snippet hello/main.cpp 1
+*/