Add Python Fibonacci calculation function

[codemie-anton]

Description

This PR adds a comprehensive Python module for Fibonacci number calculations with multiple implementation approaches.

Changes

• Created fibonacci.py with three different Fibonacci calculation functions:
  • fibonacci(n): Recursive implementation for calculating the nth Fibonacci number
  • fibonacci_iterative(n): Iterative implementation (more efficient for larger numbers)
  • fibonacci_sequence(count): Generates a list of Fibonacci numbers

Features

• Proper error handling for negative inputs
• Comprehensive docstrings for all functions
• Example usage in the __main__ block
• Both 0-indexed calculations and sequence generation

Testing

The module includes example usage that demonstrates:

• Calculating individual Fibonacci numbers (0-9)
• Using the iterative approach for larger numbers (15th position)
• Generating a sequence of the first 15 Fibonacci numbers