Improve docs

[Chingling152]

The current docs of this project is confusing and outdated.

• How to start the Project
• Architecture
  • Database
  • API Layers
  • Flows
• Infrastructure
  • External services
  • CI/CD Pipeline
• Gitflow
  • Release Branches
  • Main Branch
  • Feature Branch
  • Fix Branch
  • Hotfix Branch
• Releases