written last night prior to seeing this post:
// some false positives like "Nor," "'Hee-haw!'" (including the quotes, from theoriginal)
var enforceEndingPunct = function(lines) {
let re = /[.?!]$|^$/,
finalPunct = config.finalPunct || `.`;
// TODO: elaboration, if not defined, see what's most common? or some other heuristic
lines = lines.map((l) => re.test(l) ? l : l + finalPunct);
return lines;
};