Add ExposedList.cs to C# csproj.

spine-csharp/spine-csharp.csproj

@@ -70,6 +70,7 @@
     <Compile Include="src\AnimationState.cs" />
     <Compile Include="src\Event.cs" />
     <Compile Include="src\EventData.cs" />
+    <Compile Include="src\ExposedList.cs" />
     <Compile Include="src\IkConstraint.cs" />
     <Compile Include="src\IkConstraintData.cs" />
     <Compile Include="src\Json.cs" />
@@ -82,12 +83,12 @@
     <Compile Include="src\SlotData.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
-  <!--
-      To modify your build process, add your task inside one of the targets below and uncomment it.
-      Other similar extension points exist, see Microsoft.Common.targets.
-      <Target Name="BeforeBuild">
-      </Target>
-      <Target Name="AfterBuild">
-      </Target>
+  <!--
+      To modify your build process, add your task inside one of the targets below and uncomment it.
+      Other similar extension points exist, see Microsoft.Common.targets.
+      <Target Name="BeforeBuild">
+      </Target>
+      <Target Name="AfterBuild">
+      </Target>
     -->
-</Project>
+</Project>