Improve visibility of IPv6 related settings
IPv6 related questions come up regularly, which is a good thing, because its adoption among relays can be improved.
There was some good stuff on the list (and probably also somewhere else) that could be added at our IPv6 FAQ entry or the [[TorRelayGuide#IPv6]]. (comparing both most of it is already there, maybe we instead should try to increase the visibility a bit more?) https://torproject.org/docs/faq.html.en#IPv6 https://torproject.org/docs/faq.html.en#IPv6Relay
related: #17811 (moved) (clients), see keywords
(assigning this to the relay guide to get another opinion and happily get it back for the website)