Add Less compiler to compiling phase

[hannogrimm]

Hey there, most rc-* components are published with .css asset files. This only features .less only right now which is problematic for SASS environments. Compiling Less to CSS allows developers to import the component styles in all available CSS preprocessors.

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[cai-zhuo]

I also met this problem, my repo does not use less, but rc-select only exported less file, so i can't see any styles for this component

[yoyo837]

Conflicted.