lint / build dependencies incorrectly not marked as devDependencies

[Jessidhia]

The react-dropzone package.json includes babel-preset-env, babel-preset-stage-1, eslint-config-prettier and eslint-plugin-prettier as dependencies even though they are not used at runtime.

This results in users of published versions of the library being forced to install those packages, even though they are only needed for development. They should be devDependencies.

This may be, in turn, required by the use of a prepublish script, which happens to be run by npm on install (it's deprecated, but won't be going away for a few years yet). To work around that, it's probably better to depend on in-publish and using "prepublish": "not-in-publish || npm run prepare", "prepare": "(the current prepublish command)".

[zxlin]

To second this post, users of this lib are also warned to install prettier due to it being a peer-requirement in eslint-plugin-prettier which should be a react-dropzone dev-dependency.

Warning message:

npm WARN eslint-plugin-prettier@2.2.0 requires a peer of prettier@>= 0.11.0 but none is installed. You must install peer dependencies yourself.

Thanks!