Suggestion: Clearly document that this library is compatible with the ESP32 platform

[MicSG-dev]

I know that this library is fully compatible with the ESP32 platform. I have used this library a lot in my projects and it always works well.

My suggestion is that you document in the README.md that this library is compatible with ESP32, since some people seem to not know that this library is compatible with ESP32 and even spread misinformation claiming that the library is not compatible with ESP32.

Summary: Inform in the documentation that this library (arduino-libraries/Ethernet.h) is compatible with the ESP32 platform/architecture.