Update readme Net7 SDK required

Author: stefannikolei

README.md

@@ -64,7 +64,7 @@ If you prefer, you can compile ImageSharp yourself (please do and help!)
 
 - Using [Visual Studio 2022](https://visualstudio.microsoft.com/vs/)
   - Make sure you have the latest version installed
-  - Make sure you have [the .NET 6 SDK](https://www.microsoft.com/net/core#windows) installed
+  - Make sure you have [the .NET 7 SDK](https://www.microsoft.com/net/core#windows) installed
 
 Alternatively, you can work from command line and/or with a lightweight editor on **both Linux/Unix and Windows**: