This project was bootstrapped with Create React App.
- Add the "Add Thing" button, including the corresponding CSS.
- Make that "Add Thing" button work!
- When the checkbox is checked, mark the corresponding as completed and be sure this gets synced to Firebase and that it persists across page refreshed.
- Stop hard-coding things altogether. Use only the things that were added via the "Add Thing" button.
- Add a due date to each Thing and make sure it persists.
- Make the "remove" button work.