Document Onion Location redirects in portals
We'll need to document all the work that we are doing for legacy/trac#21952 (moved) in our websites
We should add entries for:
- Tor Browser Manual entry explaining Onion Location redirects
- Support portal entry asking "Why am I being asked to redirect to an onion service" when visiting a website
- Community Portal Onion Services section explaining the options for operators of both clearnet and onion services how they can advertise their onion service equivalent site to Tor Browser users.