Add generated targets to Design source

Author: Redth

design/source/Design.csproj

@@ -101,5 +101,6 @@
   <PropertyGroup>
     <DroidDocPaths>..\..\externals\docs\reference</DroidDocPaths>
   </PropertyGroup>
+  <Import Project="..\..\generated.targets" />
   <Import Project="..\..\packages\Xamarin.Build.Download.0.3.0\build\Xamarin.Build.Download.targets" Condition="Exists('..\..\packages\Xamarin.Build.Download.0.3.0\build\Xamarin.Build.Download.targets')" />
 </Project>