title: How to trigger AWS Codebuild When Creating Pull Request in CodeCommit?
body: <p>Our ci workflow is this</p>
  
  <ul>
  <li>run eslint in precommit</li>
  <li>push to feature branch</li>
  <li>open pull request in codecommit</li>
  <li>trigger aws code build run tests</li>
  <li>if all tests passed, merge</li>
  <li>trigger aws code deploy to deploy</li>
  </ul>
  
  <p>For now I noticed that codebuild will trigger on push. How can I make it so that it will trigger on merge request?</p>