Returns an array of content encodings accepted by the request, in order of preference. If there are no encoding supplied in the request, then ["*"] is returned, implying any encoding is accepted.

For a given set of content encodings, return the best match accepted in the request. If no content encodings match, then the function returns undefined.

NOTE: You should always supply identity as one of the encodings to ensure that there is a match when the Accept-Encoding header is part of the request.