[docs] Establish Cadence For Benchmarking Against Competitors

Dragonfly claims a significant performance increase over Redis, but the numbers appear out of date - as best I can tell from the README, Dragonfly last benchmarked against Redis in December of 2023 but Redis 8 was released in the last few weeks with claims of [significant performance improvements](https://redis.io/blog/redis-8-ga/).

Additionally, new competitors such as Valkey have entered the space but Dragonfly appears [not to have benchmarked against them at all](https://github.com/dragonflydb/dragonfly/issues/3871).

I am requesting that Dragonfly rerun its benchmarks against a recent release of both Redis and Valkey, while noting the versions used, and create a process to update the benchmarks every year or so.

I can help create some automation around running the benchmarks if necessary.

Start by reviewing the benchmark claims in the README and the related discussion in issue 3871. Determine how to rerun comparisons against recent Redis and Valkey releases, record the versions used, and define a recurring update process; done means current results and a documented cadence are established.

Written by the indexing model from the issue text.