Improve and update README.md with detailed workflow

The README.md file has been significantly updated to provide a comprehensive guide for users and contributors.

The previous version lacked detail on the repository's structure and, most importantly, the workflow for adding, testing, and promoting profiles. This could lead to confusion and errors for contributors.

This commit introduces the following improvements:

• Detailed Repository Structure: A clear, tree-like structure of the repository is now included, with explanations for each key file and directory (monit/, profiles/, active_profiles.yaml, etc.).
• Comprehensive Workflow: A new step-by-step workflow has been added, explaining the full lifecycle of a profile change:
  1. How to add a profile to the qa environment for testing.
  2. How to activate the profile using active_profiles.yaml.
  3. The requirement to validate changes on the QA Grafana dashboard (link included).
  4. The process for promoting a validated profile to the production environment.
• CI/CD Pipeline Overview: A brief explanation of the GitLab CI/CD pipeline stages (validate, push, web) is now included to give context on how changes are automatically processed.

This enhanced documentation will help ensure that contributors understand the process, leading to smoother and more consistent updates to the monitoring profiles.