Adds a preview button to a GitHub repo
UI Previewer Button adds a button to GitHub Pull Requests that allow you to go to
a preview URL for that Pull Request. You can customize how it works for every project by providing a button icon, a button text and a URL template, where the Git SHA will be inserted. Also you can add a secondary button that is less prominently featured, we use this for linking to documentation of the current build version. It works with your CI system by only using commits for which the build has successfully completed.