Update Perspex.SceneGraph.UnitTests.csproj

tests/Perspex.SceneGraph.UnitTests/Perspex.SceneGraph.UnitTests.csproj

@@ -72,6 +72,7 @@
     <Otherwise />
   </Choose>
   <ItemGroup>
+    <Compile Include="RelativeRectComparer.cs" />
     <Compile Include="RelativeRectTests.cs" />
     <Compile Include="ThicknessTests.cs" />
     <Compile Include="Media\BrushTests.cs" />
@@ -158,4 +159,4 @@
   <Target Name="AfterBuild">
   </Target>
   -->
-</Project>
+</Project>