These docs had a number of typos, and also didn't fully clarify how to
handle lists of integers for `pm-with`.
Also makes some tweaks to the user docs to make this clearer as well.
Fixes#13167.
We also document support for user IDs in the pm-with narrow operator.
Edited by tabbott to document on /api rather than in the /help page.
Fixes part of #9474.