Jump to/Autofollow another user

[edemaine]

• [x] List of users that pops down from your name
• [x] Click on user to jump to their cursor (one time)
  • [ ] Maybe also try to match view rectangle?
• [ ] Hovering over someone highlights the page they're on, and if visible, shows their view rectangle?
• [ ] Autofollow toggle
  • [ ] Draw view rectangle of the person you're following
  • [ ] Keep their cursor (plus a small area around it?) visible via panning
  • [ ] OR: Keep their view rectangle visible via panning and zooming?