Introduce SudokuType sealed class

[teogor]

This pull request introduces a new SudokuType sealed class and deprecates the old GameType enum. The new SudokuType offers several advantages:

Here's a detailed breakdown of the changes:

• Improved organization: SudokuType groups size information in a single class, providing better clarity and structure.
• Flexibility: The sealed class design allows for easy addition of new Sudoku sizes in the future.
• Clearer properties: Names and properties in SudokuType directly reflect size information, improving readability.
• Deprecation of GameType: It is marked with @Deprecated and recommended replacement with SudokuType.

Here are some specific examples of code changes:

// Before (using deprecated `GameType`)
val gameType = GameType.SixDigits // Represents a 6x6 Sudoku

// After (using new `SudokuType`)
val sudokuType = SudokuType.Sudoku6x6 // Explicit representation

For more, please view the docs: source.teogor.dev/sudoklify/sudoku-type