[Feature] Support Apache Dubbo

[EarthChen]

Apache Dubbo is a high-performance and popular RPC framework. I noticed that your project already supports gRPC, so could you also implement a corresponding set of filters for Dubbo?

[fedorka]

I believe anyone could build an implementation based on the concurrency-limits-core module.

I don't think we (the maintainers) will provide concurrency-limits-dubbo in the near future, simply because we don't currently use that framework. Is this module something that you would like to contribute?