XIAO RS485 with ESP32: Wiring & Serial Test

ESP32S Wiki: https://esp32s.com/wiki/xiao-esp32-rs485-wiring-test/

Arduino-ESP32 3.3.0 compile check; no physical bench test.
Board profile: esp32:esp32:esp32c3:CDCOnBoot=cdc
Libraries: Only Arduino-ESP32 built-in APIs are required for the supplied example.

Read the guide before wiring.
