ES Modules Support?

Hi, I'm new to grpc-web and I was checking your [Web basics tutorial](https://grpc.io/docs/tutorials/basic/web.html#generate-protobuf-messages-and-service-client-stub) when I noticed that the client code generator only supports Closure and common.js

Now that ES Modules are supported on all modern browsers, is there a chance that you'll have a generator for them? That would allow the library to be used without any build process which would be great imho