Added SFSpreadsheet to InABox.WPF

inabox.wpf/InABox.Wpf.csproj

@@ -139,6 +139,7 @@
         <PackageReference Include="Syncfusion.SfImageEditor.WPF" Version="20.2.0.46" />
         <PackageReference Include="Syncfusion.SfInput.WPF" Version="20.2.0.46" />
         <PackageReference Include="Syncfusion.SfRichTextBoxAdv.WPF" Version="20.2.0.46" />
+        <PackageReference Include="Syncfusion.SfSpreadsheet.WPF" Version="20.2.0.46" />
         <PackageReference Include="Syncfusion.Tools.WPF.Classic" Version="19.4.0.56" />
         <PackageReference Include="Syncfusion.XlsIO.Wpf" Version="20.2.0.46" />
     </ItemGroup>