A .env file containing the following values must be added to the root directory:
CONTENTFUL_SPACE_IDCONTENTFUL_ACCESS_TOKEN
These values enable the gatsby-source-contentful plugin to access the page data stored on Contentful. The same keys and values need to be provided as secrets in the GitHub repo.
The publish.yml GitHub Action is set up to build the Gatsby site on every commit to main, and then push the static files to GitHub Pages. This action is also triggered whenever a change to the Contentful site is published.