add workflow badge to README.md

Author: SimonWaldherr

README.md

@@ -1,5 +1,6 @@
 # Go Benchmarks
 
+[![test](https://github.com/SimonWaldherr/golang-benchmarks/actions/workflows/audit.yml/badge.svg?branch=master&event=push)](https://github.com/SimonWaldherr/golang-benchmarks/actions/workflows/audit.yml) 
 [![DOI](https://zenodo.org/badge/154216722.svg)](https://zenodo.org/badge/latestdoi/154216722) 
 [![Go Report Card](https://goreportcard.com/badge/github.com/SimonWaldherr/golang-benchmarks)](https://goreportcard.com/report/github.com/SimonWaldherr/golang-benchmarks) 
 [![License: MIT](https://img.shields.io/badge/License-MIT-green.svg)](https://opensource.org/licenses/MIT)