Support for board Arduino Mega

**Hi. Is any chance to add suppoort for platform board Arduino Mega to use it with ESPHome ?**

The request names Arduino Mega support for ESPHome but does not identify files, tests, or specific compatibility requirements. Start by reviewing how existing board support is organized and clarify the expected Arduino Mega hardware and feature scope. Done means Arduino Mega can be used with ESPHome and the relevant support is covered by project validation.

Written by the indexing model from the issue text.