[Issue 2265] Create splay-tree.md

[daaimah123]

📝 Description (summary of the changes)

• Three main splay operations (Zig, Zig-Zig, Zig-Zag) with detailed implementations
• Core tree operations including search, insert, and delete with full code examples
• Four hands-on activities ranging from 20-60 minutes each:
  • Trace through splaying operations
  • Implement basic tree rotations
  • Performance comparison with regular BST
  • Build a word frequency counter
• Decision framework for when to use Splay Trees vs other data structures
• Progressive complexity from basic concepts to advanced implementations
• Real-world analogies (music streaming, smart librarian)
• Step-by-step walkthroughs with visual tree representations
• Practical applications that connect to industry use cases
• Activities designed to reinforce theoretical concepts through coding practice

🎁 Acceptance Criteria

• All splay operations (Zig, Zig-Zig, Zig-Zag) are correctly implemented
• Tree rotation functions handle parent pointer updates correctly
• Content is structured with proper heading hierarchy
• Code examples include explanatory comments
• Complex concepts are broken down into digestible sections
• Visual learners can follow tree transformation diagrams
• Multiple learning styles are accommodated through varied activity types

⚙️ Related Issue

Issue Number: #2265

🍏 Type of Change

New Topic Outline

[monikkaelyse]

Approving with minor suggestions