Add camelCase option for css-loader

[roman-holovin]

Resolves #376

Docs: https://github.com/webpack-contrib/css-loader#camelcase

This is not a breaking change, given css

.my-header { color: blue}

will result in such object

{
    my-header: "src-pages----index-module---my-header---2Xmei", 
    myHeader: "src-pages----index-module---my-header---2Xmei"
}

[KyleAMathews]

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[mingaldrichgan]

Would this be a breaking change if a CSS file already has, e.g. both .my-header and .myHeader defined with different styles?

[KyleAMathews]

@mingaldrichgan since this is opt-in, it wouldn't be a breaking change. You can only break things if you enable it :-)

[KyleAMathews]

Oh nvm, this isn't an option. @Dantix yeah, this would break things. So to get this in, you'd need to make this optional using plugin options.

[jquense]

I don't think this is being made configurable here, but turning it on by default?

[roman-holovin]

Thanks, I see your point.
Problem is that CSS loader configuration is used by a lot of other plugins, like gatsby-plugin-less, they all leverage cssModulesConfig function. So if for example we choose to extend it, so it can provide additional options to loader, all code, which currently uses it, will need to be updated also.

Since I'm only getting grasp on gatsby and this is going to be not so trivial change as I've anticipated, I would like you to give your opinion ( @KyleAMathews @jquense ) on how this problem can be approached in an extensible and non-breaking way.

[KyleAMathews]

I'm not sure this is worth worrying about right now. I believe when we switch to webpack 3, these sorts of changes will be simpler.

If you want to research more a possible fix @Dantix that'd be great but I don't see camelCase or not being a big deal for using css modules.