Draft: style: fix formatting of files using code formatters

As mentioned on the web page Why Prettier?, using code formatters help us to format code and to "stop all the on-going debates over styles":

By far the biggest reason for adopting Prettier is to stop all the on-going debates over styles. It is generally accepted that having a common style guide is valuable for a project and team but getting there is a very painful and unrewarding process. People get very emotional around particular ways of writing code and nobody likes spending time writing and receiving nits.

This merge request introduces formatters that we can run using pre-commit run -a.