Added Sudoku Solver using Backtracking in Python

[kavyasrik7]

-->Overview
This pull request adds a Python implementation of a Sudoku Solver using the backtracking algorithm.
It also includes functionality to generate a random Sudoku puzzle each time the program runs,
making the project interactive and fun to experiment with.

--> Features

• Generates a random 9x9 Sudoku puzzle with adjustable difficulty (empty cells count).
• Solves the puzzle using an efficient backtracking approach.
• Displays both the unsolved and solved Sudoku boards in a clean console format.
• Beginner-friendly code with simple variable names and clear structure.

--> Tech Stack

• Language: Python
• Algorithm: Backtracking

--> Hacktoberfest 2025 Contribution
This contribution adds a new algorithm implementation to the repository and aims to help
beginners understand how backtracking can be used in solving constraint satisfaction problems like Sudoku.

--> Testing

• Verified locally in VS Code.
• Outputs correct solutions for multiple random board generations.

**I hope you find this contribution helpful! Looking forward to your feedback.