Created the todo app in C++ 17

[brodante]

This pull request introduces a new Qt-based Todo List application in the CPP/todo.cpp file. The application allows users to add and remove tasks through a graphical user interface.

New Features:

• Qt Application Setup:

  • Added includes for necessary Qt classes such as QApplication, QMainWindow, QLabel, QVBoxLayout, QWidget, QLineEdit, QPushButton, QListView, QStringListModel, and QMessageBox. ([CPP/todo.cppR1-R96](https://github.com/fineanmol/Hacktoberfest2024/pull/7986/files#diff-0b6c595284b3f863ba11db49bda3c1de22ec2b20a7a496c2c94e44f8c84089c4R1-R96))
  • Created a TodoListApp class inheriting from QMainWindow to set up the main window and central widget. ([CPP/todo.cppR1-R96](https://github.com/fineanmol/Hacktoberfest2024/pull/7986/files#diff-0b6c595284b3f863ba11db49bda3c1de22ec2b20a7a496c2c94e44f8c84089c4R1-R96))

• Task Management:

  • Implemented a QStringListModel to manage the list of tasks. ([CPP/todo.cppR1-R96](https://github.com/fineanmol/Hacktoberfest2024/pull/7986/files#diff-0b6c595284b3f863ba11db49bda3c1de22ec2b20a7a496c2c94e44f8c84089c4R1-R96))
  • Added a QListView to display tasks and disabled editing directly in the view. ([CPP/todo.cppR1-R96](https://github.com/fineanmol/Hacktoberfest2024/pull/7986/files#diff-0b6c595284b3f863ba11db49bda3c1de22ec2b20a7a496c2c94e44f8c84089c4R1-R96))
  • Added QLineEdit for task input and QPushButton for adding and removing tasks. ([CPP/todo.cppR1-R96](https://github.com/fineanmol/Hacktoberfest2024/pull/7986/files#diff-0b6c595284b3f863ba11db49bda3c1de22ec2b20a7a496c2c94e44f8c84089c4R1-R96))

• User Interaction:

  • Connected the "Add" button to a slot (add_task) that adds a new task to the list if the input is not empty, otherwise shows a warning message. ([CPP/todo.cppR1-R96](https://github.com/fineanmol/Hacktoberfest2024/pull/7986/files#diff-0b6c595284b3f863ba11db49bda3c1de22ec2b20a7a496c2c94e44f8c84089c4R1-R96))
  • Connected the "Remove" button to a slot (remove_task)