Add support for avoiding widows

I would like to avoid the last 2 words in a paragraph from appearing on the last line by themselves.

For now I've been hacking around this by manually wrapping the last few words in a with a class that typeset is configured to ignore (to avoid soft-hyphens) and manually replacing spaces between those words with  .

Was this functionality intentionally omitted? If not, I'm happy to take a shot at implementing it myself.