New Python Program: To-Do List Manager

Hello Python enthusiasts! Let's enhance our repository with a To-Do List Manager implemented in Python. This beginner-friendly task involves creating a program that allows users to add tasks, mark tasks as completed, view the to-do list, and remove completed tasks. This task will showcase data structures, loops, and conditional statements in Python.

**Tasks:**
- Implement functions to add tasks, mark tasks as completed, view the to-do list, and remove completed tasks.
- Store tasks in a list or dictionary data structure.
- Provide user-friendly menus and prompts for each operation.
- Handle errors gracefully, such as accessing tasks that don't exist.
- Ensure completed tasks can be removed from the list.

**Guidelines:**
- Use Python 3.x for the program.
- Implement functions for each operation (add_task, mark_completed, view_tasks, remove_completed, etc.).
- Include comments in your code to explain the logic and functionality.
- Test the program thoroughly, covering various scenarios including adding, completing, and removing tasks.

**Example:**

```
Welcome to the To-Do List Manager!

1. Add Task
2. Mark Task as Completed
3. View To-Do List
4. Remove Completed Tasks
5. Exit

Select an option: 1
Enter task: Complete Python project
Task 'Complete Python project' added successfully!

1. Add Task
2. Mark Task as Completed
3. View To-Do List
4. Remove Completed Tasks
5. Exit

Select an option: 3
To-Do List:
1. [ ] Complete Python project

...
```

**How to Contribute:**
1. Fork this repository.
2. Create a new Python file for the To-Do List Manager: `todo_manager.py`.
3. Write the Python program following the specified tasks and guidelines.
4. Test the program thoroughly to ensure it functions correctly.
5. Commit your changes: `git commit -m "Add To-Do List Manager program"`
6. Push to your branch: `git push origin add-todo-manager`
7. Open a pull request to this repository.

Your contribution will provide users with a practical tool for managing tasks. Thank you for creating this useful Python program for our repository!