feat: Rewrite root module, define listeners, draft MockManager

[almeida1492]

This proposal uses both methods addEventListener and sendMessage to create intercommunication between the actual client application and the mock manager interface. By the use of this technique, it is possible to override the MSW handlers, change the mocked data at runtime, and keep the code of the Mock Manager and the client app separated into two different components trees.

To verify the behavior, do the following:

1. Reinstall the dependencies, because I've updated react;
2. Run the dev server with yarn run dev;
3. Open it up at http://localhost:1234/;
4. Submit the form;
5. See the message returned by the worker at the HTTP call interception (This is the original response message);
6. Click on "Open Mock Manager";
7. Enter some data in the JSON editor and submit it;
8. Return to the previous app (the one with the name-and-surname form) and try to submit the form again;
9. See the mocked data overridden by the data you've just entered in the Mock Manager form.