docs(changelog): add initial changelog.md

Added CHANGELOG.md following the Keep a Changelog format.
- Documented the initial release (v1.0.0) of PHP DevSuite.
- Included details on:
  - Supported technologies: Laravel, WordPress, Magento, and more.
  - Pre-built Docker Compose setup with PHP, Nginx, MySQL, PostgreSQL, Elasticsearch, OpenSearch, RabbitMQ.
  - Pre-configured Docker images for PHP, Nginx, and other services.
  - Utility scripts for easier container management.
  - Security and configuration enhancements, including .env.example and optimized Nginx settings.

This change provides a structured versioning history for future updates.