make eslint happy

Created by: katjaq

What is the current behaviour?

Thanks to @omgitsjoao , we now have xo and can eslint our BrainBox code by running npm test. I just ran it – and it gives a greaaaaaaat number of errors you can choose from 😊

What is the expected or desired behaviour?

We would be super happy about any fixes to decrease this number little by little by little :)