Cover removable-media permissions in handbook

Dear FreeBSD documentation whizzes,

I've only been daily-driving FreeBSD for a little less than a year, so I'm
not knowledgeable enough to be writing documentation, but from the
perspective of someone who has encountered and overcome beginners'
problems, I have a suggestion that I think will help smooth the way for
others:

Chapter 8 of the FreeBSD handbook, which covers installing desktop
environments, should also cover setting up some basic device permissions
most desktop users want (or refer them to a different chapter for this if
more appropriate).

At present following the instructions to install KDE in section 8.2 results
in a system where you have a graphical file manager but cannot use it to
mount and unmount CDs, DVDs, and thumb drives -- actions that are
deservedly privileged but that many desktop users need and expect to be
able to do. I imagine the steps for other desktops have the same issue.

Users such as myself with existing experience in some other UNIX-like
environment will correctly guess that the missing features are due to
permissions they haven't set up, but they won't know which permissions or
which man pages to look at. KDE in particular requires not just appropriate
permissions set in /dev/ but also entries added to a config file for polkit
-- a subject the Handbook currently does not cover at all.

Adding a how-to for this common task will both rescue the user experience
for people not yet deep enough into the technical world to immediately
think, "I should Google for some arcane config entry that fixes this," and
encourage people to follow actual best practices like giving enhanced
privileges to administrative groups like operator or wheel rather than just
removing all security guardrails on removable media.

Thanks,
Timothy Gaskell