Merge pull request #139 from baywet/docs/overlay-dotnet

adds a link to overlay dotnet

Author: lornajane

README.md

@@ -25,6 +25,7 @@ If you are looking for tools to use with Overlays, try these:
 - [oas-patch CLI](https://github.com/mcroissant/oas_patcher)
 - [oas-overlay-java](https://github.com/IBM/oas-overlay-java)
 - [Specmatic](https://specmatic.io/) - [Docs](https://docs.specmatic.io/documentation/contract_tests.html#overlays)
+- [BinkyLabs.OpenApi.Overlays - dotnet](https://github.com/BinkyLabs/openapi-overlays-dotnet)
 
 (Is something missing from the list? Send us a pull request to add it!)