Setup may be simpler

I find the setup pretty complex in a typical developer environment. Things could be a lot more straightforward.

For me, the best approach would be to use [build_runner](https://dart.dev/tools/build_runner) like [built_value](https://pub.dev/packages/built_value). You add the dependency to the plugin in your project pubspec, and then use the `pub run build_runner watch` to generate the message and service classes from .proto files in project.

The protoc should also be included.

As a reference, it's actually how it works in the .NET world : you add your NuGet package and you're fine.