feat: exports as an `{Array}`

[plantvsbirds]

this should be very useful in some cases when I need some resource both be required, loaded dynamically(using babel or css loader) and their source code displayed(using raw loader).

my proposal would be adding an optional param to multi called options, and a boolean value asArray within the object. In this way packages depending on this won't be broken and people can enjoy this feature.

if this interests you please check my changes at https://github.com/plantvsbirds/multi-loader

[michael-ciniawsky]

@plantvsbirds PR welcome :) it's better for further discussion

[plantvsbirds]

I will wait for your latest PR. btw I am actually new to webpack loaders and still can't think of a good way passing the option object without breaking existing usage. any idea?