Request: Widow control (widont)

This is a great library! Thanks so much for maintaining it.

I'd love to see an option for controlling [widows](https://en.wikipedia.org/wiki/Widows_and_orphans). For instance [typogr.js uses the "widont" pattern](https://github.com/ekalinin/typogr.js#widont) of replacing the space between the last two words in a block with ` `.

(Typographically a widow is actually a single line on a wrapped paragraph rather than a single word on a wrapped line, but on the web the usage seems to be mostly about not leaving a single word, since multicolumn layouts are less common.)