Mention ESP32 in supported hardware?

[danb35]

The documentation page for supported hardware (https://github.com/thorrak/fermentrack/blob/master/docs/source/hardware.rst) lists only ESP8266- and Arduino-based BrewPi controllers. But it looks like, despite its name, brewpi-esp8266 has supported ESP32 boards since March, and that release note says that the ESP8266 won't be supported in future releases. Seems that would be worth an update to the docs.