Updating index.md

Author: github-actions[bot]

index.md

@@ -36,6 +36,10 @@ You can use the [Arduino-ESP32 Online Documentation](https://docs.espressif.com/
 
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+**APIs compatibility with ESP8266 and Arduino-CORE (Arduino.cc) is explained [here](https://docs.espressif.com/projects/arduino-esp32/en/latest/libraries.html#apis).**
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 * [Getting Started](https://docs.espressif.com/projects/arduino-esp32/en/latest/getting_started.html)
 * [Installing (Windows, Linux and macOS)](https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html)
 * [Libraries](https://docs.espressif.com/projects/arduino-esp32/en/latest/libraries.html)