update readme

README.md

@@ -5,4 +5,10 @@ This repo implements
 - Goldilocks Field mod `2^64 - 2^32 + 1`
 - Goldilocks quadratic extension over `x^2 + 1`
 - Goldilocks cubic extension over `x^3 - x - 1`
+
 Traits are compatible with `ff 0.13.0`.
+
+### Benchmark
+```
+cargo bench
+```