normalizeCharset

Ensures that only a single `@charset` is present in the CSS file, and moves it to the top of the document. This prevents multiple, invalid declarations occurring through naïve CSS concatenation. Note that *by default*, new `@charset` rules will not be added to the CSS.

Example

Input

.box {
    content: "©";
}
@charset "utf-8";
@charset "utf-8";

Output

@charset "utf-8";
.box {
    content: "©";
}