Create actions.yml so it can be used locally with act

[mariusgreve]

To be able to run this action locally through act it requires an action.yml file to describe the action.
This file is fairly simple and should just need to reference the Dockerfile https://docs.github.com/en/free-pro-team@latest/actions/creating-actions/metadata-syntax-for-github-actions

name: ...
description: ...
author: ...
runs:
  using: docker
  image: Dockerfile