Add OnMessageDeleted moderator action

[vaindil]

This adds the PubSub event for mods deleting messages. For reference, an example parsed version of the data payload is below.

{
  "data": {
    "type": "chat_login_moderation",
    "moderation_action": "delete",
    "args": [
      "alexanderthegreat200",
      "VoteYea VoteYea",
      "a5092c19-1d59-4480-8a32-c94794579272"
    ],
    "created_by": "pokelec",
    "created_by_user_id": "109743169",
    "msg_id": "",
    "target_user_id": "89653350"
  }
}

[swiftyspiffy]

Looks good, thanks!