Sudoku Update - Drag and Drop, Hotkeys, and More

The Sudoku game has been updated with a drag and drop feature for placing numbers into cells. Hotkeys have been improved: Shift + N toggles Notes mode, Shift + D toggles Delete mode, and Shift + H uses a Hint. An option to show or hide notes has been added. Additionally, users can now download or print the Sudoku board as an image, including the initial board, current board, and solved board (if the user has solved it).