State

As we add more commands, the statefulness of our program is going to increase. We're going to shove all that state into a State object. There are a few goals for this object:

Give each command handler to the commands registry (looking at you help command)
Give the commands access to the readline interface created with createInterface so that the exit command can clean up after itself

In the future there will be even more shared state, and we want a simple function signature that all the callbacks can conform to, namely:

callback: (state: State) => void;

Assignment

Create a state.ts file.
Move your definition of the CLICommand type into this file, and update the callback property to use the more flexible signature from above.
Export a new State type from this file, it should contain the readline interface and the commands registry. Here's a hint about how to get those types:

import { createInterface, type Interface } from "readline";

Export a new function called initState. Move the logic that creates the readline interface and the commands registry into this function. It should return an initialized State object.
Update main.ts to initialize a State object using the new function, and pass it into your REPL loop. The REPL loop should now use the state's readline interface and commands registry.
Update the exit command handler to .close() the readline interface before exiting the program.
Update the help command handler to use the commands registry via the State object.

Now that we've done all this... nothing's changed! Our code should still work the exact same way. Womp womp. Welcome to refactoring! Refactoring is actually a super important skill that you'll spend a lot of time doing as a developer. It's all about updating the structure (but not behavior) of your code to make it easier to read, maintain, and extend.

Run and submit the CLI tests.