onStatus ({ key = '', cbGID } = {}, cb) {
    this._registerListener('status', { 0: key }, null, cbGID, cb)
  }
Register a handler to be called on each message for the desired status
feed.

@param {object} opts - options
@param {string} opts.key - key of feed to listen on
@param {string|number} [opts.cbGID] - callback group ID
@param {Function} cb - callback
@see WSv2#subscribeStatus