Several minor changes, adding a full functioning Home Assistant Thermostat

Now the Advanced_Thermostat.ino in the example directory is a ready-to-go thermostat specially designed for Home Assistant with MQTT integration. Just set your credentials in the program, flash it to e.g. an ESP32-S2 mini, connect the wires of your existing thermostat to the shield and add a Home Assistant Automation to send the room temperature to the thermostat. The Thermostat (MQTT HVAC) Climate integration will 'automagically' appear, together with sensors for boiler setpoint temperature, router RSSI signal level, a flame ON / OFF sensor, and, if your boiler supports it, water pressure, a flow temperature, return temperature, relative modulation percentage and Domestic Hot Water sensor.