add hardware

README.md

@@ -15,10 +15,13 @@ wasi-i2c is currently in [Phase 1](https://github.com/WebAssembly/WASI/blob/main
 ### Portability Criteria
 
 WASI-I2C must have at least an independent implementation for the following platforms: 
-- Linux (ARM)
-- Linux (RISC-V)
-- RTOS (Zephyr or FreeRTOS)
-- Microcontroller implementation (Cortex M4 as a lowerbound)
+| Platform | Architecture | Reference Hardware |
+| ------------- | ------------- | ------------- |
+| Linux  | ARM  | Raspberry Pi 3 Model B |
+| Linux  | RISC-V  | ESP32 |
+| RTOS (Zephyr or FreeRTOS) | ARM32 | Nucleo F412ZG &
+
+Furthermore, implementations shouldn't take up all the available RAM.
 
 ### Introduction