Add prettier package and apply config to all files

[stffffn]

The existing prettier config wasn't applied to any of the files. I installed prettier as a dev dependency and let it run over all files. I also added two scripts for checking and automatically fixing:

prettier: npm run prettier
prettier:fix: npm run prettier:fix

I stumbled upon this when I wanted to fix something else - I hope this is fine.

[gabipurcaru]

good catch; I didn't get around to setting up prettier correctly, thanks for the help.