Action to create pages in the correct place

Right now, the user must manually create the site after the branches are set up. Luckily, [GitHub has a method for creating sites through the API](https://docs.github.com/en/rest/reference/repos#create-a-github-pages-site), so we can add a small action that does that if the page does not exist.

This will definitely make it easier for contributors

Start by reading the existing actions in this repository and the linked GitHub Pages API documentation. Identify the action entry point and how it can check whether a site exists before creating one. Done means contributors no longer need to manually create the site after branches are set up, while existing sites are left unchanged.

Written by the indexing model from the issue text.