Update TodoList.jsx to use useDispatch

[joequery]

This is an update of the TodoList example provided for demonstrating React modules. There are two main parts to this update:

1. Fixed a bug where clicking the div associated with a todo Item would correctly toggle the completed state internally, but the checkbox would not update.
2. Refactored the TodoList logic to use useDispatch over useState. This purifies the component and moves the state management logic to a central location (the reducer function).