title: User input in github actions (specify repo branch, etc)
body: <p>I want to create a github action to create an integration test environment. We already have a dockerized script which can do this, however, the environment is made up of 2+ repositories. So, in order to make this effective during development, we'd need to specify the branches of the other repos.</p>
  
  <p>For example, let's say I have a PR in repo: frontend, branch: my-feature-brach. It requires repo: backend, branch: their-feature-branch. I'd like to kick off a build from my PR where it uses the branch of that PR (in the frontend repo), and ask me which branch to use for the backend repo.</p>
  
  <p>Is this possible?</p>