Design a Swing-based Java application that allows users to create and manage a personal to-do list. The application should have a user-friendly graphical user interface (GUI) with features such as adding new tasks, editing existing tasks, marking tasks as completed, and deleting tasks. The application should also support saving and loading the to-do list to/from a file, as well as sorting tasks by due date or priority. The main window of the application should have a JList component to display the tasks, along with JTextFields and JButtons for adding, editing, marking as completed, and deleting tasks. The application should also have a menu bar with options to save the to-do list to a file in JSON format, load a saved to-do list from a file, and sort the tasks in the list either by ascending due date or by priority as determined by a user- defined priority score. The layout and design of the GUI should be user-friendly and aesthetically pleasing. Please provide a clear and concise description of the task, including specifications such as the format of the saved file, the sorting algorithm to be used, and the criteria for determining task priority.