Add docs for service filtering

[onobc]

See #207

[Meijuh]

I can confirm service filtering is working. However, filtering out the "health service" and "reflection service" might be a more valuable example, if you agree not having them on in-process servers is good practice:

return (serviceDefinition, __) ->
        !HealthGrpc.SERVICE_NAME.equals(serviceDefinition.getServiceDescriptor().getName())
            && !ServerReflectionGrpc.SERVICE_NAME.equals(
                serviceDefinition.getServiceDescriptor().getName())

Looking forward to a 0.9.0 release.

[onobc]

I can confirm service filtering is working. However, filtering out the "health service" and "reflection service" might be a more valuable example, if you agree not having them on in-process servers is good practice:

return (serviceDefinition, __) ->
        !HealthGrpc.SERVICE_NAME.equals(serviceDefinition.getServiceDescriptor().getName())
            && !ServerReflectionGrpc.SERVICE_NAME.equals(
                serviceDefinition.getServiceDescriptor().getName())

Looking forward to a 0.9.0 release.

Good suggestion @Meijuh . PTAL at the result here

[Meijuh]

LGTM!😀