Add link to windows issue

README.markdown

@@ -70,7 +70,7 @@ It will also generate client implementations of `PingService`; currently [Twirp]
 - `npm install ts-proto`
 - `protoc --plugin=./node_modules/.bin/protoc-gen-ts_proto --ts_proto_out=. ./simple.proto`
   - (Note that the output parameter name, `ts_proto_out`, is named based on the suffix of the plugin's name, i.e. "ts_proto" suffix in the `--plugin=./node_modules/.bin/protoc-gen-ts_proto` parameter becomes the `_out` prefix, per `protoc`'s CLI conventions.)
-  - On Windows, use `protoc --plugin=protoc-gen-ts_proto=.\node_modules\.bin\protoc-gen-ts_proto.cmd --ts_proto_out=. ./simple.proto`
+  - On Windows, use `protoc --plugin=protoc-gen-ts_proto=.\node_modules\.bin\protoc-gen-ts_proto.cmd --ts_proto_out=. ./simple.proto` (see [#93](https://github.com/stephenh/ts-proto/issues/93))
   - Ensure you're using a modern `protoc`, i.e. the original `protoc` `3.0.0` doesn't support the `_opt` flag
 
 This will generate `*.ts` source files for the given `*.proto` types.