Add not about supported platforms

README.md

@@ -12,6 +12,16 @@ involves compiling rust -> C library, and linking that library to the Go code.
 For ergonomics of the user, we will include pre-compiled libraries to easily
 link with, and Go developers should just be able to import this directly.
 
+## Supported Platforms
+
+Since this package includes a rust prebuilt dll, you cannot just import the go code,
+but need to be on a system that works with an existing dll. Currently this is Linux
+(tested on Ubuntu, Debian, and CentOS7) and MacOS. We have a build system for Windows,
+but it is not supported by the wasmer singlepass backend which we rely upon for gas
+metering.
+
+*Note: Windows is not supported currently*
+
 ## Design
 
 Please read the [Documentation](./spec/Index.md) to understand both the general