workflow: Update README with Go reference (#63)

Author: andrewwormald

README.md

@@ -9,6 +9,7 @@
         <a style="padding: 0 5px" href="https://sonarcloud.io/summary/new_code?id=luno_workflow"><img src="https://sonarcloud.io/api/project_badges/measure?project=luno_workflow&metric=sqale_rating"/></a>
         <a style="padding: 0 5px" href="https://sonarcloud.io/summary/new_code?id=luno_workflow"><img src="https://sonarcloud.io/api/project_badges/measure?project=luno_workflow&metric=vulnerabilities"/></a>
         <a style="padding: 0 5px" href="https://sonarcloud.io/summary/new_code?id=luno_workflow"><img src="https://sonarcloud.io/api/project_badges/measure?project=luno_workflow&metric=duplicated_lines_density"/></a>
+        <a style="padding: 0 5px" href="https://pkg.go.dev/github.com/luno/workflow"><img src="https://pkg.go.dev/badge/github.com/luno/workflow.svg" alt="Go Reference"></a>
     </div>
 </div>