Follow-up from "Allow using launcher-direct on non-default seat with non-root user"

The following discussion from !494 (merged) should be addressed:

• @marius.vlad0 started a discussion: (+1 comment)

  Reviewed-by: Marius Vlad marius.vlad@collabora.com

  Btw, I think this is pretty cool to have/use. Also, there are other users of launcher-direct.

  I've discovered some kind of quirk while using it and in revolves around multiple outputs for that DRM-node. With udev you can tell libinput, which output to assign a specific input by using ENV{WL_OUTPUT}. Had a to dig a bit in libpinput to find out this.

  Anyway, think maybe a follow-up doc page for this non-root launcher-direct might be useful to have, or an example with the udev rule?

Make the doc. Maybe a page in the Sphinx docs?