This commit adds an mdbook for rayhunter documentation in `doc`, and
actions workflows to publish that documentation to github pages.
This commit configures actions to publish to pages via artifact uploads,
but but can be adjusted to publish based solely on a branch.[0]
This was chosen to allow for future flexibility in generating multiple
outputs (such as a single page html document or pdf).
[0] https://docs.github.com/en/pages/getting-started-with-github-pages/configuring-a-publishing-source-for-your-github-pages-site
