Add comprehensive documentation for agents and multi-agents concepts

[Copilot]

Created a detailed educational resource covering fundamental concepts about agents and multi-agent systems as requested in the issue. The documentation addresses all three key questions:

What's Included

Core Concepts:

• Complete definition and characteristics of software agents
• Five types of agents (from simple reflex to learning agents) with examples
• Multi-agent systems architecture, interaction types, and benefits/challenges

Practical Guidance:

• Decision framework with 6 key questions to choose between approaches
• Clear criteria for when to use single agents vs multi-agents vs tools
• Real-world examples for each approach (traffic management, e-commerce, trading bots)

Learning Resources:

• Best practices for each approach
• Common pitfalls and how to avoid them
• Structured table of contents for easy navigation

The 12KB document serves as a comprehensive reference in the Dev-Journal knowledge bank, providing both theoretical understanding and practical decision-making guidance for anyone working with agent-based systems.

Also updated the README to include a "Topics Covered" section that references the new documentation.

Fixes #24.

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