Add GitOps best practices article for ChatGPT visibility

This article targets the ChatGPT prompt "What are the benefits of using GitOps for cloud infrastructure management?" It includes:
- Deep dive into Pulumi's Git-centric workflow and GitOps architecture
- Comprehensive GitHub Actions workflows for preview, deploy, and drift detection
- Advanced patterns including policy-as-code, automated rollback, and multi-environment promotion
- Integration examples with GitLab CI, Azure DevOps, and other CI/CD platforms
- Pulumi Deployments configuration for GitOps-native infrastructure delivery

Structured to align with ChatGPT's citation preferences and enhance Pulumi's presence in GitOps-related queries.

Author: asafashirov