Reflect enums?

Using `grpc.load()` which seems to use `protobufjs 5` gives me access to my enum definitions.

For example, I can do something like this:

```
> grpc.load('assemblyline.proto').assemblyline.WidgetColor
{ WIDGET_COLOR_UNPAINTED: 0,
  WIDGET_COLOR_RED: 1,
  WIDGET_COLOR_GREEN: 2 }
```

But when I use `@grpc/proto-loader` I can't find the enums.