Enforce code formatting

[christiaanwesterbeek]

With my recent PR's I noticed code formatting is not enforced by something like prettier in this repo. I tried my best to format my changes to adhere to the current formatting, but it's not ideal. It makes for easier collaboration (and smaller PR's) if code formatting is enforced.

I propose to use prettier with the following .prettierrc config that adhere best to the current code formatting.

{
    "singleQuote": true,
    "tabWidth": 2,
    "trailingComma": "es5",
    "useTabs": false
}

[christiaanwesterbeek]

Or better even; Let's be on par with react-admin on code formatting and copy-paste their prettier config.

https://github.com/marmelab/react-admin/blob/master/.prettierrc.js

[scheiblr]

That is a great point. We should definitely do that. Currently, I'm pretty busy, I will invest some time, as soon as possible. Also, then I will check your PRs. I already coarsly looked into that, so please stay patient :)

[scheiblr]

added into branch improvements. This will be part of next release (which will probably still need some time). Thus, please stay patient ;) I will postpone your very valuable PRs, i.e. we have to incorporate them into the improved (future) version, once I made major progress with it.