Update Tor wiki and migrate muon issues to this repo

[diracdeltas]

• https://github.com/search?utf8=%E2%9C%93&q=is%3Aopen+is%3Aissue+org%3Abrave+label%3Ator%2Fleakproofing&type=Issues < all these issues should be migrated here
• https://github.com/brave/browser-laptop/wiki/Using-Tor-in-Brave should be migrated to this repo since it's no longer editable
• The "known leaks" link should be updated to point to this repo instead of muon https://github.com/brave/browser-laptop/wiki/Using-Tor-in-Brave#are-private-tabs-using-tor-perfectly-private
• https://support.brave.com/hc/en-us/articles/360018121491 should point to the wiki page (or the github page of known leaks) so technical users can learn about what the leaks are.

[riastradh-brave]

• Audit all protocols for leaks in Tor mode and block them or redirect them through Tor muon#521 ⟶ Audit all protocols for leaks in Tor mode and block them or redirect them through Tor #4252
• certificate fetches should use Tor or be disabled in Tor mode muon#520 ⟶ certificate fetches should use tor or be disabled in tor windows #4245
• audit for DNS leaks in Tor mode muon#519 ⟶ Add tests for DNS leaks in Tor #4257
• Browser process's system request context should be handled differently under Tor muon#518 ⟶ Browser process's system request context should be handled differently under Tor #4254
• Test rig for identifying leaks muon#466 ⟶ Test rig for identifying leaks #4256
• Audit path from browser making URL requests down to contacting SOCKS proxy muon#465 ⟶ Audit path from browser making URL requests down to contacting SOCKS proxy #4255