Implement Event Emitter

An Event Emitter is a design pattern that allows objects to emit named events and register listeners for those events. This is fundamental to understanding how many JavaScript libraries and frameworks work.

Problem Statement

Implement a custom EventEmitter class with the following methods:

• on(event, listener) - Register a listener for an event
• off(event, listener) - Remove a listener for an event
• emit(event, ...args) - Emit an event with optional arguments
• once(event, listener) - Register a one-time listener