Create doc site

[acobster]

Acceptance Criteria

• a new /docs directory with the minimum files for a Gitbook setup: README.md, SUMMARY.md, GLOSSARY.md, book.json (see Conifer's docs for reference)
• Basic doc styles according to the Groot Brand Develop Groot Brand #23
• DNS for grootthe.me domain pointing to Netlify
• Netlify set up to build automatically on releases published (i.e. when a new tag is pushed) to github.com/sitecrafting/groot