chore: update build badge to GH Actions

README.md

@@ -1,6 +1,6 @@
 # Dockerised Pact Broker
 
-[![Build Status](https://travis-ci.org/pact-foundation/pact-broker-docker.svg?branch=master)](https://travis-ci.org/pact-foundation/pact-broker-docker)
+[![Release Docker image](https://github.com/pact-foundation/pact-broker-docker/actions/workflows/release_image.yml/badge.svg)](https://github.com/pact-foundation/pact-broker-docker/actions/workflows/release_image.yml)
 
 This repository contains a Dockerized version of the [Pact Broker][pact-broker]. You can pull the `pactfoundation/pact-broker` image from [Dockerhub][pact-broker-docker]. If you're viewing these docs on Dockerhub, here is a link to the [github repository][github].