rikapo

This PR fixes the url path of Korean document from 'kr' to 'ko'. All languages are using language codes in url path, except Korean. The language code of Korean is...

Hello, According to the [API document](https://lokeshdhakar.com/projects/color-thief/#api), getPalette() function is supposed to return an array containing colors, but in fact, also returns null. ([src/color-thief-node.js line 87](https://github.com/lokesh/color-thief/blob/1c70277219c7bcfcd5ea4481cdb17136077c4fc1/src/color-thief-node.js#L87)) It would be great if...