Write a class template that behaves like a vector but can notify registered parties of internal state changes. The class must provide at least the following operations:
- Various constructors for creating new instances of the class
- operator= to assign values to the container
- push_back() to add a new element at the end of the container
- pop_back() to remove the last element from the container
- clear() to remove all the elements from the container
- size() to return the number of elements from the container
- empty() to indicate whether the container is empty or has elements
operator=, push_back(), pop_back(), and clear() must notify others of the state changes. The notification should include the type of the change, ...
