Update README.md

Author: reliak

README.md

@@ -2,4 +2,10 @@ MoonPdf
 =======
 
 MoonPdf is a WPF-based PDF Viewer that uses the MoonPdfLib library.
-It uses MuPdf for the rendering of the PDF pages.
+
+The MoonPdfLib contains a WPF control that can be included in your application.
+An example for the inclusion is the MoonPdf app (see excerpt below)
+```xml
+<Window xmlns:mpp="clr-namespace:MoonPdfLib;assembly=MoonPdfLib" ...>
+  <mpp:MoonPdfPanel Background="LightGray" ViewType="SinglePage" PageDisplay="ContinuousPages" PageBorderThickness="0,2,4,2" AllowDrop="True"/>
+</Window>