Reworking deployment flow

[lewisjared]

We need to streamline the build and deploy process as the huge number of files makes it difficult to see what really changed.

I'm proposing that we move to using a GitHub action to build and deploy the required files and HTML (https://docs.github.com/en/pages/getting-started-with-github-pages/configuring-a-publishing-source-for-your-github-pages-site#publishing-with-a-custom-github-actions-workflow). This would involve no longer tracking the docs/primap-hist/data directory as that is populated during the build process.

We should also support pull request previews. These pull request previews build and deploys so that the updates can be checked as part of the PR. See https://github.com/marketplace/actions/deploy-pr-preview

Definition of done

• Verify downloading and building can be performed on the CI
• Add GH actions to build
• Add GH action to generate deploy previews

Alternative Option

Use netlify like the other CR websites, but that maybe overkill