Merge pull request #11 from godotengine/vs2019-required

README: Mention that only VS 2019 is supported

Author: neikeq

README.md

@@ -1,9 +1,11 @@
 # Godot C# extension for Visual Studio
+
 Visual Studio extension for the Godot game engine C# projects.
 
 ## Requirements
 
 - **Godot 3.2.3** or greater. Older versions of Godot are not supported and do not work.
+- **Visual Studio 2019**. VS 2017 or earlier are not supported.
 
 ## Features