Reword "ESP-IDF as Component" (espressif#7812)

I think "Arduino as an ESP-IDF component" or just "As ESP-IDF component" instead of  "ESP-IDF as Component" is more correct way to name the link.

1. "ESP-IDF as Component" would imply that ESP-IDF is some sort of library for Arduino, which is (IMO) misleading, because it's true the other way around.
2. It's written as "Arduino as an ESP-IDF component" on the webpage it points to as well.

- Also I removed the capitalization from "Component" as I have not found a reason why is it capitalized.

README.md

@@ -33,7 +33,7 @@ You can use the [Arduino-ESP32 Online Documentation](https://docs.espressif.com/
 * [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)
-* [ESP-IDF as Component](https://docs.espressif.com/projects/arduino-esp32/en/latest/esp-idf_component.html)
+* [Arduino as an ESP-IDF component](https://docs.espressif.com/projects/arduino-esp32/en/latest/esp-idf_component.html)
 * [FAQ](https://docs.espressif.com/projects/arduino-esp32/en/latest/faq.html)
 * [Troubleshooting](https://docs.espressif.com/projects/arduino-esp32/en/latest/troubleshooting.html)