Reorganize the repo to be publishable to the marketplace

[unamashana]

Thanks @smeijer for the action! Can we reorganize the repo to be able to publish the action to the marketplace? The instructions are at https://docs.github.com/en/actions/creating-actions/publishing-actions-in-github-marketplace#publishing-an-action.

TLDR;

When you plan to publish your action to GitHub Marketplace, you'll need to ensure that the repository only includes the metadata file, code, and files necessary for the action. Creating a single repository for the action allows you to tag, release, and package the code in a single unit. GitHub also uses the action's metadata on your GitHub Marketplace page.