Replace Azure DevOps badge with Github Actions

We switched from Azure DevOps to GitHub actions in #4295
This will now update the badge to show the build status in the README for the latest "push" event on the "master" branch

README.md

@@ -1,6 +1,6 @@
 # NUnit 3 Framework #
 
-[![AppVeyor Build status](https://ci.appveyor.com/api/projects/status/3xfkxtnkrts1x06q/branch/master?svg=true)](https://ci.appveyor.com/project/CharliePoole/nunit/branch/master) [![Azure Pipelines Build Status](https://nunit.visualstudio.com/NUnit/_apis/build/status/NUnit%20Framework/NUnit%20Framework%20CI?branchName=master)](https://nunit.visualstudio.com/NUnit/_build/latest?definitionId=11&branchName=master) [![NuGet Version and Downloads count](https://buildstats.info/nuget/NUnit)](https://www.nuget.org/packages/NUnit)
+[![AppVeyor Build status](https://ci.appveyor.com/api/projects/status/3xfkxtnkrts1x06q/branch/master?svg=true)](https://ci.appveyor.com/project/CharliePoole/nunit/branch/master) [![Github Actions Build Status](https://github.com/nunit/nunit/actions/workflows/continuous_integration.yml/badge.svg?branch=master&event=push)](https://github.com/nunit/nunit/actions/workflows/continuous_integration.yml) [![NuGet Version and Downloads count](https://buildstats.info/nuget/NUnit)](https://www.nuget.org/packages/NUnit)
 
 [![Follow NUnit](https://img.shields.io/twitter/follow/nunit.svg?style=social)](https://twitter.com/nunit) [![Slack](https://img.shields.io/badge/chat-on%20Slack-brightgreen)](https://join.slack.com/t/nunit/shared_invite/zt-jz58jw68-Led8y3WH4n2a~Y5WjuOpKA) [![nunit-discuss Google Groups](https://img.shields.io/badge/mailing%20list-nunit--discuss-blue.svg)](https://groups.google.com/forum/#!forum/nunit-discuss) [![NUnit issues marked with "help wanted" label](https://img.shields.io/github/issues/nunit/nunit/help%20wanted.svg)](https://github.com/nunit/nunit/issues?q=is%3Aopen+is%3Aissue+label%3A%22help+wanted%22) [![NUnit issues marked with "good first issue" label](https://img.shields.io/github/issues/nunit/nunit/good%20first%20issue.svg)](https://github.com/nunit/nunit/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22)