Add C# graphql-net-client (graphql#285)

Hey, since I couldn't find any resources how to query GraphQL endpoints from C# specifically I created an example. It might not be the most sophisticated or feature-complete implementation, but it could help people to get started using GraphQL on .NET.

Author: Benjamin Kniffler

site/code/index.html.js

@@ -359,7 +359,11 @@ Code that executes a hello world GraphQL query with \`graphql-clj\`:
 
 ### Swift / iOS
 
-- [Apollo iOS](http://dev.apollodata.com/ios/) ([github](https://github.com/apollostack/apollo-ios)): A GraphQL client for iOS that returns results as query-specific Swift types, and integrates with Xcode to show your Swift source and GraphQL side by side, with inline validation errors.
+  - [Apollo iOS](http://dev.apollodata.com/ios/) ([github](https://github.com/apollostack/apollo-ios)): A GraphQL client for iOS that returns results as query-specific Swift types, and integrates with Xcode to show your Swift source and GraphQL side by side, with inline validation errors.
+
+### C# / .NET
+
+  - [graphql-net-client](https://github.com/bkniffler/graphql-net-client): Basic example GraphQL client for .NET.
 
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