add valkey benchmark

[araera111]

Could you please provide the benchmark results for Valkey and Dragonfly?

[binaryfire]

@centminmod Valkey 8.0 has a new architecture and is multi-threaded. Very curious to know how it compares. If their benchmarks are to be believed, it should be the fastest option now: https://valkey.io/blog/unlock-one-million-rps/