Provide support for building in Intellij Rider

[bukowa]

Follow up to https://github.com/3F/DllExport/issues/141#issuecomment-608103235

I just tried using DllExport for a simple task. Found the repository and while using Rider landed on this topic. Building in Visual Studio just works. I have no idea what is really happening and what steps should one perform to investigate this topic because of my little to non knowledge about C# and build chains. Maybe someone can provide more context.