eBus support for Vaillant (and others) heaters

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

Please add support for eBus protocol used on various heaters/boilers like Vaillant or ProTherm brand. It needs voltage shifter as it uses the voltage level of 9-20V, but communication is pure UART.

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

Genuine WIFI enabled controller for ProTherm hearts is rather expensive, costs like $150 and it is closed-ware. I would much rather use something open source and much more smart, like EPSHome is.

**Additional context**

Proper implementation exists as a separate project, but it deserves to be part of the ESPHome project, to give users another usage possibility. https://github.com/slavikb/BaiMon