Suggest adding an example when armeria + spring is used for docs.

[eottabom]

It would be nice to have an example when you used armeria + spring for docs. I think it will be used a lot as an amaria + spring combination.

For example

When using GrpcService (https://armeria.dev/docs/server-grpc) Register the ArmeriaServerConfigurator with a bean, It would be nice if the examples I use were added.

As below..

@Configuration
public class GrpcServerConfig {

    private final MyHelloService myHelloService;

    public ArmeriaServerConfig(MyHelloService myHelloService) {
        this.myHelloService= myHelloService;
    }

    @Bean
    public ArmeriaServerConfigurator armeriaServerConfigurator() {
        return (serverBuilder) -> {

            GrpcServiceBuilder grpcServiceBuilder = GrpcService.builder()
                    .addService(this.myHelloService);

            serverBuilder.service(grpcServiceBuilder.build());
        };
    }
}