v15a - ESP32-S2 Bugfix

The v15 release of BrewPi-ESP uses the latest ESP32-Arduino framework - unfortunately - has a bug in the IIC implementation for the ESP32-S2. Since the S2 was intended to be used with an IIC LCD every character printed (or "printed" - the actual presence of a screen is irrelevant!) to the screen causes a delay which locked down the whole controller.

This release is specifically for the ESP32-S2, and changes nothing other than reverting to a version of the Arduino framework based on a prior version of ESP-IDF. This should dramatically speed up builds for the ESP32-S2, and is a recommended upgrade for all users of the controller.