Improved display of commentaries in TEI Publisher

[mromanello]

• add small headers indicating different region types in a page (commentary, critical text, app crit)
• keep line breaks in the critical text (both in the display and in the TEI encoding)
• display footnote text in a smaller font size
• static markdown About page

[pletcher]

Line breaks might be a bit trickier than anticipated: I'm not sure where to find them in the regions of a CanonicalCommentary, so we might have to insert line breaks between words based on the word index?