This change updates the frontend so that the modal state is not stored
inside Redux but instead is stored using the useState hook. This
simplifies the design of the modal components.

This change updates the web frontend to use Next.js instead of Create
React App (CRA). Next.js enables the possibility of rendering pages on
the server side (which reduces the time to first frame) and overall
provides a better development experience.

Future commits will try to futher optimize the implementation for
Next.js.

This change refactors the frontend to use hooks for obtaining state
within the Redux store as opposed to using Higher-Order Components
(HOCs). This eliminates a lot of clutter in the components.

This change updates the project structure to become flattened.
Previously, the simulator, frontend and API each lived into their own
directory.

With this change, all modules of the project live in the top-level
directory of the repository. This should improve discoverability of
modules of the project.