Add max packet size to CONNECT

x.x.x.x Max Packet Size A Two Byte (16-bit) Integer representing the Maximum Packet Size the Client is willing to accept. If the Maximum Packet Size is set to 0, no limit on the packet size is imposed beyond the limitations in the protocol as a result of the remaining length encoding and the protocol header sizes.                Non-normative comment It is the responsibility of the application to select a suitable Maximum Packet Size value if it chooses to restrict the Maximum Packet Size.   The packet size is the total number of bytes in an MQTT Control Packet, as defined in section 3.1. The Client uses the Maximum Packet Size to inform the Server that it will not process packets exceeding this limit.   The Server MUST NOT send packets exceeding Maximum Packet Size to the Client  [MQTT-3.1.2-24] . If a Client receives a packet whose size exceeds this limit, this is a Protocol Error, the Client uses DISCONNECT with Reason Code 0x95 (Packet too large), as described in section 3.2.8.   Where a Packet is too large to send, the Server MUST discard it without sending it and then behave as if it had completed sending that Application Message  [MQTT-3.1.2-25] .    Non-normative comment Where a packet is discarded without being sent, the Server could place the discarded packet on a ‘dead letter queue’ or perform other diagnostic action. Such actions are outside the scope of this specification.