[FR] Support DIY with ESP32-Dev and AD8232

[aenertia]

Hi there ; I would like to use Heartypatch code base for my DIY'd ecg running on a clone esp32-dev board and ad8232.

The main challenges are some of the hardcoded assummptions about the max3000 adc chip. It would be great to refactor things a little so that any adc could be dropped in as a pin def/header def and reuse everything else.

[aenertia]

the AD8232 just returns a reading over Analog ; ideally I just want a data structure where this reading can be returned into and then the rest of the code can remain the same; after undefining the max/spi stuff.