Mozilla Thing API implementation

**Describe the problem you have/What new integration you would like**

As a user of the ESPHome library, I would like to have the option to use the Mozilla Thing API as an alternative to the Home Assistant API to use custom built devices with the Mozilla GateWay.

**Please describe your use case for this integration and alternatives you've tried:**

Sadly, their Home Assistant alternative only supports that API for communicating with devices. No MQTT, no REST, ... 😢 Or a flexible tool like the ESPHome 😭

**Additional context**

The people at Mozilla came out with a very versatile & broad spectrum API description which they are aiming to make a W3C standard. It currently exists as a draft at https://iot.mozilla.org/specification/ and their libraries are available for the most popular languages including Arduino C and Python.