Fix linting and add tests

[textbook]

I noticed the linting and tests didn't actually pass, so fixed them up. I also added a test that makes sure the component does what demo.gif shows it doing. This entailed:

• Making the minimal fixes for ESLint/Prettier
• Installing some additional dependencies for testing purposes
• Making the back and close buttons more accessible so it's easy to select them from tests

[dulajkavinda]

hello there, everything looks fine but i noticed an issue in the Done.js file. It increases height when transitioning from the other UIs. Check it from this video