Inverse of parseWords. Interleaves words with seps; added words
get " " gaps, removed words keep the original trailing separator.
A zero-word original (seps.length === 1) treats its one entry as
lead only, so words append after it without double-counting as trail.
Inverse of
parseWords. Interleaves words withseps; added words get" "gaps, removed words keep the original trailing separator. A zero-word original (seps.length === 1) treats its one entry as lead only, so words append after it without double-counting as trail.