Document prefs in 000-tor-browser.js and 001-base-profile.js

Mullvad are going to want to communicate with their users the difference between Firefox ESR 102 and Privacy Browser. To start with, we should ( after #40783 (closed) and #40014 (closed) ) ensure each pref (or batch of prefs) are associated with a gitlab ticket and have a description of what pref does and why we set it.