Add support water heater by MQTT discovery

For proper integration of Redmond kettles into a home assistant, a mqtt discovery water heater is required.
Now a good project uses the climate so that the kettle can automatically appear in the home assistant.

But we all need Water Heater mqtt discovery.
Since the kettle class is not yet available.

it will be a small step towards the integration of a large number of IOTs.

Others of them

Tasmota also has water heaters!

What? i dont understand