Update the index page of the documentation

src/xlsx/doc/src/qtxlsx-index.qdoc

@@ -25,23 +25,79 @@
 
 /*!
     \title Qt Xlsx
-    \page qtxlsx-index.html
+    \page index.html
     \brief Qt Xlsx provides functionality for handling .xlsx files.
 
-    .xlsx is a zipped, XML-based file format developed by Microsoft for
-    representing spreadsheets.
+    QtXlsx is a library that can write Excel files. It doesn't require
+    Microsoft Excel and can be used in any platform that Qt5 supported.
 
     \section1 Getting Started
 
-    Qt Xlsx provides classes for writing .xlsx files. To include the definitions
-    of the module's classes, use the following directive:
+    \section2 Usage(1): Use source code directly
 
-    \snippet doc_src_qtxlsx.cpp 0
+    The package contains a qtxlsx.pri file that allows you to integrate
+    the component into applications that use qmake for the build step.
 
-    To link against the module, add this line to your qmake \c
-    .pro file:
+    1. Download the source code.
 
-    \snippet doc_src_qtxlsx.pro 1
+    2. Put the source code in any directory you like. For example, 3rdparty:
+
+    \code
+    |-- project.pro
+    |-- ....
+    |-- 3rdparty\
+    |     |-- qtxlsx\
+    |     |
+    \endcode
+
+    3. Add following line to your qmake project file:
+
+    \code
+    include(3rdparty/qtxlsx/src/xlsx/qtxlsx.pri)
+    \endcode
+
+    \note If you like, you can copy all files from *src/xlsx* to your application's source path. Then add following line to your project file:
+
+    \code
+    include(qtxlsx.pri)
+    \endcode
+
+    4. Then, using Qt Xlsx in your code
+
+    \code
+    #include "xlsxdocument.h"
+    int main()
+    {
+        QXlsx::Document xlsx;
+        xlsx.write("A1", "Hello Qt!");
+        xlsx.saveAs("Test.xlsx");
+        return 0;
+    }
+    \endcode
+
+    \section2 Usage(2): Use Xlsx as Qt5's addon module
+
+    \note Perl is needed.
+
+    1. Download the source code.
+
+    2. Put the source code in any directory you like. At the toplevel directory run
+
+    \code
+    qmake
+    make
+    make install
+    \endcode
+
+    The library, the header files, and the feature file will be installed to your system.
+
+    3. Add following line to your qmake's project file:
+
+    \code
+    QT += xlsx
+    \endcode
+
+    4. Then, using Qt Xlsx in your code
 
     \section1 References
     \list