add more explicit notice this is an unofficial library

Author: OkGoDoIt

README.md

@@ -1,6 +1,6 @@
 # C#/.NET SDK for accessing the OpenAI GPT-3 API, ChatGPT, and DALL-E 2
 
-A simple C# .NET wrapper library to use with OpenAI's GPT-3 API.  More context [on my blog](https://rogerpincombe.com/openai-dotnet-api).
+A simple C# .NET wrapper library to use with OpenAI's GPT-3 API.  More context [on my blog](https://rogerpincombe.com/openai-dotnet-api).  This is an unofficial wrapper library around the OpenAI API.  I am not affiliated with OpenAI and this library is not endorsed or supported by them.
 
 ## Quick Example