doc: benchmarks/rich/README.md

benchmarks/rich/README.md

+# RICH Benchmarks
+
+## Setup
+- Build `reconstruction_benchmarks` with `cmake`
+  - Builds code in `src/` and `include/` to a library
+    - Benchmarks are designed as independent algorithms, similar to reconstruction algorithms
+    - Algorithm inputs are PODIO collections produced from reconstruction, and the output
+      is typically a set of `ROOT` plots
+  - Builds executable `benchmark_rich_reconstruction`, which runs any or all of the benchmark
+    algorithms and streams any plots to an output `ROOT` file
+
+## Running
+- Run the benchmark executable using the wrapper script `run_benchmark.rb`
+  - Run with no arguments for usage guide
+  - This script can run simulation, reconstruction and/or benchmarks
+  - Run `benchmark_rich_reconstruction` to just run the benchmark algorithms