Add comprehensive Circuit Breaker Pattern documentation

[Copilot]

This PR adds detailed documentation explaining the Circuit Breaker design pattern to the Dev-Journal repository. The documentation provides a comprehensive overview of this important resilience pattern used in distributed systems.

What's Added

New file: circuit-breaker-pattern.md

• Complete explanation of what the Circuit Breaker pattern is and why it's used
• Detailed breakdown of the three states: Closed, Open, and Half-Open
• Real-world scenarios and problem examples (e.g., e-commerce payment service failures)
• Working Python implementation example with practical usage
• Benefits, trade-offs, and guidance on when to use/avoid the pattern
• References to popular libraries (Netflix Hystrix, Polly, Resilience4j, etc.)

Updated: README.md

• Added "Topics Covered" section for better content discoverability
• Linked to the new circuit breaker documentation

Key Features of the Documentation

The documentation is structured as an educational resource that covers:

• Problem Definition: Cascading failures, resource exhaustion, poor user experience
• Solution Mechanism: How the pattern monitors and protects against service failures
• Implementation: Practical code example showing the pattern in action
• Real-world Context: When and where to apply this pattern effectively

This addition aligns with the repository's purpose as a learning journal and knowledge bank, providing a thorough reference for understanding this critical design pattern in modern distributed systems.

Fixes #3.

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