Support of named CSS imports (`css-loader`'s `namedExport`)

[birdofpreyru]

css-loader's namedExport option (which is default in some cases since its v7.0.0) requires to import CSS stylesheets (when the mapping is needed in JS code) like this

import * as S from "./style.css";

// or, I guess
import { a, b, c } from "./style.css";

// Instead of just
import S from "./style.css";

Thus, we need to update this Babel plugin to support named CSS imports (which it currently does not).