CAN's add command should fire a COMMAND_ADD event

CAN's add command should trigger a COMMAND_ADD event, with the name provided as an argument.

Backlinks

• Can should inform the user of the add command when a new note is in the scratchfile
  • CAN's inform-add handler should listen to NOTE_EXISTENCE, informing the user of the add command. The add command should exist at this point and should fire a COMMAND_ADD event with the user-passed name.