Added Getting started for ASP.NET Core 6 (#561)

Author: snakefoot

README.md

@@ -30,6 +30,7 @@ Please check [platform support](https://github.com/NLog/NLog/wiki/platform-suppo
 
 ### ASP.NET Core
 
+- [Getting started for ASP.NET Core 6](https://github.com/NLog/NLog/wiki/Getting-started-with-ASP.NET-Core-6)
 - [Getting started for ASP.NET Core 5](https://github.com/NLog/NLog/wiki/Getting-started-with-ASP.NET-Core-5)
 - [Getting started for ASP.NET Core 3](https://github.com/NLog/NLog/wiki/Getting-started-with-ASP.NET-Core-3)
 - [Getting started for ASP.NET Core 2](https://github.com/NLog/NLog/wiki/Getting-started-with-ASP.NET-Core-2)