Migrate EV3 library docs to "modules"

[RichDom2185]

The EV3 docs are currently hosted at https://docs.sourceacademy.org/EV3 (source files: ev3.js, EV3_README.md).

In line with the move to modularise remote execution (related issues: source-academy/modules#196, source-academy/frontend#2412), let us migrate these docs to be part of the modules documentation at https://source-academy.github.io/modules/documentation.