Implements a serial terminal on an epdiy ePaper controller.

Quickstart:

1. Build and flush: idf.py build && idf.py flash -b 921600
2. Write to the TTY, e.g. script -f /dev/ttyUSB0

Known Issues:

• With ESP-IDF 4.0, there is seems to be an issue with the UART leading to missing / delayed data in some cases. Seems to be gone in 4.1. Enabling UART ISR in IRAM might help.

• st is licensed under MIT/X Consortium License (see main/LICENSE).