Merge pull request #1606 from EricAtMSFT/implementation_update

Adding C# comment reader that converts to OpenAPI.NET doc tooling.

Author: darrelmiller

IMPLEMENTATIONS.md

@@ -74,3 +74,4 @@ These tools are not endorsed by the OAI.
 | slush-vertx | [github/pmlopes/slush-vertx](https://github.com/pmlopes/slush-vertx) | Java, Kotlin & Groovy | Generate server skeleton for [Vert.x Web API Contract](http://vertx.io/docs/#web) and API Client based on [Vert.x 3 Web Client](http://vertx.io/docs/#web)
 | WebSphere Liberty | [Download jar](https://developer.ibm.com/wasdev/downloads/) | Java EE | Generates OpenAPI v3 documentation from Java EE applications |
 | swagger-node-codegen | [github/fmvilas/swagger-node-codegen](https://github.com/fmvilas/swagger-node-codegen) | Node.js | Generates a Node.js/express server, but also has a template engine for creating any templates needed. |
+.NET-C#-Annotations | [github/Microsoft/OpenAPI-NET-CSharpAnnotations](https://github.com/Microsoft/OpenAPI.NET.CSharpAnnotations) | dotnet | Convert your native C# comments/annotation XML from your API code into a OpenAPI document object. |