allow to set socket timeout

[vladak]

The socket timeout is set in

Adafruit_CircuitPython_MiniMQTT/adafruit_minimqtt/adafruit_minimqtt.py

Line 267 in 67e0ade

sock.settimeout(timeout)

however _get_connect_socket() is called without the timeout argument

Adafruit_CircuitPython_MiniMQTT/adafruit_minimqtt/adafruit_minimqtt.py

Line 447 in 67e0ade

self._sock = self._get_connect_socket(self.broker, self.port)

which means the timeout is always 1 - assuming this is in seconds, the doc does not say:

Adafruit_CircuitPython_MiniMQTT/adafruit_minimqtt/adafruit_minimqtt.py

Line 217 in 67e0ade

:param int timeout: Desired socket timeout

It would be nice if the socket timeout could be set in the MQTT instance.

After issues like #81 or #110 are fixed, it will be useful.