Add README with API documentation and update server port

[Copilot]

Adds basic documentation for the simple Express.js server and updates the server configuration.

Changes

• README.md: Added project documentation covering installation, running the server, and API endpoint details
• .gitignore: Added package-lock.json since project uses yarn
• index.js: Changed server port from 3002 to 6666

API Documentation

GET http://localhost:6666/
Response: "Hello world!"
Status: 200 OK

Created from VS Code.

Original prompt

Hello

Created from VS Code.

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[osortega]

@copilot Change to port 6666

[Copilot]

@copilot Change to port 6666

Changed the server port from 3002 to 6666 in both index.js and the documentation in README.md (commit 9c583e4).