Add techniques folder to organize problem-solving patterns

[Copilot]

This PR adds a new techniques folder to the root directory of the repository to organize various problem-solving techniques and patterns for LeetCode problems.

Changes Made

• ✅ Created techniques/ folder in the root directory
• ✅ Added techniques/README.md with initial documentation
• ✅ Committed changes to the main branch

Purpose

The techniques folder will serve as a centralized location for documenting and organizing common algorithmic patterns, data structures, and problem-solving approaches used across different LeetCode solutions. This will help developers:

• Quickly reference solution patterns
• Understand common techniques used in competitive programming
• Organize knowledge systematically

File Structure

/
├── techniques/
│   └── README.md
├── README.md
├── graph-clone-explanation.md
├── longest-palindrome-solution.md
├── longest-substring-solution.md
└── two-sum-solution.md

The folder is now ready for future contributions of technique documentation and pattern examples.

This pull request was created as a result of the following prompt from Copilot chat.

Ana (main) branch üzerinde, kök dizinde 'techniques' adında bir klasör oluştur. Bu klasörün eklenmesi ve commitlenmesi sağlansın.

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