index.md: Update YAML file header

- Key 'published' was blank, so Jekyll wasn't publishing it
Update _config.yml
Update .gitignore
Edit span doc-id, leaving only 'version'
Style refinements

- Add body margin-top
- Edit format of span doc-id
Updates for v1.5.0

- Update bibliography
- Edit section 'Disclaimers'
- Edit section 'Highlight'