Add Docker Compose deployment for WebRTC server stack

[Axingx]

Background

The current README explains how to manually deploy the WebRTC server components, including AppRTC, Collider, coturn, Nginx, and HTTPS configuration. A Docker Compose setup would make the project easier to reproduce and test.

Goal

Add a Docker Compose based deployment that can start the main components with documented environment variables.

Tasks

• Add docker-compose.yml
• Add .env.example
• Document required ports
• Document TLS/domain requirements
• Verify deployment on Ubuntu 22.04 or 24.04

Acceptance Criteria

A developer can clone the repository, configure .env, and start the basic WebRTC server stack using Docker Compose.