Fix the action name in the /draw command

[jbassagana]

The /draw command should return a key-value pair as described in the following examples.

Propose a draw:

{
  "/draw": {
    "action": "propose"
   }
}

Decline a draw:

{
  "/draw": {
    "action": "decline"
   }
}

Accept a draw:

{
  "/draw": {
    "action": "accept"
   }
}

See #148

Happy coding!