A few small fixes:
- Better documentation as per #31
- footnotes.scss spun off as per #30
- New placeholder icon as per #33
- File type styles as per #34
- Monospace type for `code` tag
- Fix `figcaption` margins on small screens
- Add basic css file for external use (e.g. Marked.app preview)
- Civil Footnotes added as a basic theme feature