Add support for named exports

[mrmckeb]

Is your feature request related to a problem? Please describe.
As raised by @fmal, named exports aren't available at present.

Describe the solution you'd like
In theory, with the camelCase option, set to "only" (both in this plugin and CSS Loader), named exports could be created alongside or in place of the default export. This may need another option, such as namedExports (boolean).

Describe alternatives you've considered
The plugin could always export named exports for valid strings, but this would create a confusing developer experience - which is why it may need to be opt-in.

[mrmckeb]

@fmal Would the above solution be good for your needs?

[fmal]

@mrmckeb sure, your proposal of making this opt-in and effective only when camelCase is switched on, sounds like the best solution. Thanks for asking 😃