Mention ChainSync Client benchmark

Author: geo2a

docs/website/contents/for-developers/Benchmarks.md

@@ -1,11 +1,22 @@
 # Consensus benchmarks
 
 We are in the process of adding component level microbenchmarks for Consensus.
+
+We check for regressions in performance on CI.
+
+## Mempool Benchmark
+
 We started with microbenchmarks for adding transactions to the mempool. The
 mempool benchmarks can be run using the following command.
 
 ```sh
 cabal new-run ouroboros-consensus:mempool-bench
 ```
 
-We check for regressions in performance on CI. We might publish benchmark results in this site shortly.
+## ChainSync Client Benchmark
+
+To aid the refactoring of the ChainSync client, we added a benchmark for it in [PR#823](https://github.com/IntersectMBO/ouroboros-consensus/pull/823). The benchmark could be invoked as follows:
+
+```sh
+cabal new-run ouroboros-consensus:ChainSync-client-bench -- 10 10
+```