CAN's link command should enumerate links for the last rendered note

When no argument is given to the link command, it should render the links from the last rendered note. The links should be enumerated as they are when the link command is passed a name.

The last rendered note should be stored by the link-rendering handler (inspired by the actor model - no other code needs to be aware of this state)

Backlinks

• Links in CAN
  • without an argument, the link command should enumerate the last rendered note