How to keep existing linebreaks after punctuation

[maelle]

See ropensci/roweb3#946 (comment) by @steffilazerte (thank you Steffi!)

A challenge is not confusing these informative linebreaks with the ones automatically added after 80 characters. Maybe the presence of punctuation before the break is a good criterion.

[Bisaloo]

It might be useful to keep this behind a setting because the Carpentries now recommend having 1 sentence = 1 line rather than mid-sentence breaks, as traditional semantic linebreaks recommend.

carpentries/sandpaper-docs#241