Added SharpJson to project.

spine-csharp/spine-csharp.csproj

@@ -100,12 +100,11 @@
     <Compile Include="src\IUpdatable.cs">
       <SubType>Code</SubType>
     </Compile>
-    <Compile Include="src\Json.cs">
-      <SubType>Code</SubType>
-    </Compile>
+    <Compile Include="src\Json.cs" />
     <Compile Include="src\MathUtils.cs">
       <SubType>Code</SubType>
     </Compile>
+    <Compile Include="src\SharpJson.cs" />
     <Compile Include="src\Skeleton.cs">
       <SubType>Code</SubType>
     </Compile>